Effects of repeated intra-articular hyaluronic acid on cartilage degeneration evaluated by T1ρ mapping in knee osteoarthritis.

OBJECTIVES: Intra-articular injection of hyaluronic acid (IAHA) has been used for the treatment of knee osteoarthritis (OA), but its effectiveness remains controversial. This study analyzed knee OA over time by magnetic resonance imaging (MRI) T1ρ mapping to objectively evaluate whether long-term repeated administration of IAHA influences cartilage degeneration. METHODS: Sixty knees of 60 patients [58.3 ± 12.5 years (mean ± standard deviation)] who had multiple T1ρ mapping images were retrospectively analyzed. We calculated the T1ρ values of the medial femorotibial cartilage and classified changes in degenerative areas over time into 3 groups: Improvement, No Change, and Deterioration. RESULTS: Average time between 2 MRI scans was 7.6 ± 1.2 months. The number of IAHA administrations was 15.5 ± 21.3, 8.39 ± 7.19, and 5.80 ± 7.49 in the Improvement, No Change, and Deterioration groups, respectively. Body mass index and number of IAHA administrations were significant factors causing change in the area of degeneration (p < .05) independent of age, sex, Kellgren-Lawrence grade, and posterior horn meniscus tears. CONCLUSION: Cartilage degeneration may be improved with a higher number of administrations of IAHA, based on T1ρ mapping results. This highlights the possibility of increased treatment effectiveness of IAHA for knee OA with repeated administrations.

Quantitative Assessment of Liver Function by Using Gadoxetic Acid-enhanced MRI: Hepatocyte Uptake Ratio.

Purpose To determine whether hepatocyte uptake ratios derived at gadoxetic acid-enhanced MRI correlate with quantitative measures of liver function and can help to identify contraindication to major hepatectomy. Materials and Methods Between August 2016 and October 2016, 50 study participants with chronic liver disease or cirrhosis underwent liver MRI at 3.0 T including T1 mapping and elastography. Liver function was quantitatively assessed by using the indocyanine green retention test (ICG R15). T1 maps were obtained by using the Look-Locker sequence before and 10 minutes after gadoxetic acid administration (0.025 mmol/kg). The relationship between ICG R15 and the following MRI parameters was evaluated: pre- and postcontrast T1 values of the liver, hepatocyte uptake ratio representing the amount of contrast media solely taken into hepatocytes, liver volume, and degree of enhancement at the common bile duct. Diagnostic performance of the hepatocyte uptake ratio to identify patients with ICG R15 greater than 20% (ie, contraindication to hepatectomy) was compared with other parameters by using areas under the receiver operating characteristic curve. Results Hepatocyte uptake ratio showed a negative correlation with ICG R15 r of -0.78 (P < .001). In participants with chronic liver disease or Child-Pugh class A, those with ICG R15 of 20% or less showed higher hepatocyte uptake ratio than those with ICG R15 greater than 20% (P < .001). Hepatocyte uptake ratios demonstrated better performance for helping to detect ICG R15 greater than 20% than did liver volume (area under the curve, 0.96 vs 0.70; P = .01). Conclusion Hepatocyte uptake ratios are negatively correlated with liver function as measured by indocyanine green retention test and provide acceptable diagnostic performance for helping to identify participants who have contraindications to major hepatectomy. © RSNA, 2018 Online supplemental material is available for this article. See also the editorial by Reeder in this issue.

Robust visualization of middle cerebral artery main trunk by enhanced acceleration-selective arterial spin labeling (eAccASL) for intracranial MRA.

PURPOSE: A new sequence for intracranial MRA is developed, named enhanced acceleration-selective arterial spin labeling (eAccASL), to improve main artery visualization at middle cerebral artery (MCA). The aim of this study is to assess the visualization improvement using eAccASL, compared with the previously developed AccASL. METHODS: eAccASL and AccASL were performed in 8 healthy volunteers and images were compared between the 2 sequences. One patient with Moyamoya disease was evaluated by eAccASL and time of flight. For the volunteer images, vessel visualization was assessed by measuring the contrast-to-noise ratio between MCA M1 to M4 and white matter and by counting the peripheral arteries. Venous artifact level was assessed by measuring the contrast-to-noise ratio between the confluence of the sinuses and white matter and by evaluating cortical vein visualization. For the patient images, qualitative assessment of peripheral and collateral vessel visualization was conducted. RESULTS: In the MCA main trunk, higher arterial signal intensity, with reduced flow void, was observed in eAccASL compared with AccASL. Contrast-to-noise ratios of M1 to M3 for eAccASL were significantly higher than those of AccASL. There was no significant difference between AccASL and eAccASL for venous artifact. CONCLUSION: eAccASL could produce better MCA main trunk visualization compared with AccASL, while maintaining good venous signal suppression.

Non-contrast enhanced 4D intracranial MR angiography based on pseudo-continuous arterial spin labeling with the keyhole and view-sharing technique.

PURPOSE: 4D dynamic MR angiography (4D-MRA) using pseudo-continuous arterial spin labeling (pCASL), combined with Keyhole and View-sharing (4D-PACK) for scan acceleration, is introduced. Its validity for arterial inflow dynamics visualization was investigated through comparison with 4D-pCASL and contrast inherent inflow enhanced multiphase angiography (CINEMA). METHODS: Six healthy volunteers were included in the study. The arterial transit time (ATT) in 4D-PACK was measured at multiple regions in middle cerebral artery (MCA), and Pearson's correlation coefficient with ATT in 4D-pCASL was calculated. The contrast-to-noise ratio (CNR) in 4D-PACK was measured in four MCA segments and compared with that in 4D-pCASL and CINEMA. Arterial visualization in 4D-PACK was assessed qualitatively in patients with moyamoya disease and arteriovenous malformation by comparing with CINEMA. RESULTS: 4D-PACK achieved a 36% scan time reduction compared with 4D-pCASL. The correlation coefficient for ATT measured by 4D-pCASL and 4D-PACK was greater than 0.96. The CNR was significantly higher using 4D-PACK compared with CINEMA in the M4 segment (P < 0.01). In patient examinations, the flow in the collateral artery or draining vein was better visualized in 4D-PACK compared with CINEMA. CONCLUSION: 4D-PACK accelerates 4D-pCASL, shows similar inflow dynamics as 4D-pCASL and shows better peripheral visualization compared with CINEMA. Magn Reson Med 80:719-725, 2018. © 2018 International Society for Magnetic Resonance in Medicine.

Bone morphological factors influencing cartilage degeneration in the knee.

OBJECTIVES: Morphological features of the distal femur and proximal tibia associated with cartilage degeneration are unknown. This study aimed to elucidate local anatomical parameters of the knee which correlate with articular cartilage degeneration using MRI T1ρ mapping. METHODS: This study involved 200 subjects with knee pain (mean age, 48.7 years; range, 14-80 years) with no severe osteoarthritic changes on plain X-ray. T1ρ values were measured in the regions of interest on the surface layer of the cartilage on mid-coronal images of the femorotibial joint. Assessment of medial and lateral posterior tibial slope (MTS, LTS) and medial and lateral femoral condylar offset ratio (MFCOR, LFCOR) was performed using sagittal proton density-weighted imaging. Morphological assessment of posterior root and horn of menisci was also performed according to a modified Whole Organ Magnetic Resonance Imaging Score (WORMS) of the knee. RESULTS: Multiple regression analysis revealed that a decrease in MTS was associated with increased T1ρ values in the medial tibia, independent of age, osteoarthritic changes on plain X-ray, femur-tibia angle (FTA), and posterior medial meniscal lesions. CONCLUSIONS: Shallow MTS correlates with cartilage degeneration in symptomatic patients. This parameter could help in understanding the etiology of osteoarthritis in the early stage. Future kinematic studies will be needed to confirm our findings.

Quantitative Liver Function Analysis: Volumetric T1 Mapping with Fast Multisection B1 Inhomogeneity Correction in Hepatocyte-specific Contrast-enhanced Liver MR Imaging.

Purpose To determine whether B1 inhomogeneity-corrected volumetric T1 maps of gadoxetic acid-enhanced liver magnetic resonance (MR) imaging are able to demonstrate global liver function and functional heterogeneity in patients with cirrhosis and to investigate their relationship with the development of hepatic insufficiency and decompensation. Materials and Methods This institutional review board-approved retrospective study with waiver of informed consent included 234 consecutive patients who underwent gadoxetic acid-enhanced liver MR imaging, including B1 inhomogeneity-corrected volumetric T1 mapping. For all patients, T1 relaxation times of the liver and liver volumes were measured on T1 maps. Liver T1 and functional liver volume-to-weight ratio (liver volume divided by liver T1 and the patient's weight) were compared between Child-Pugh class A and class B cirrhosis. Associations between serum markers, MR parameters, hepatic insufficiency, and decompensation were investigated by using Cox proportional hazards analysis. Results Patients with Child-Pugh class B disease showed significantly longer liver T1 (548.2 msec ± 257.7 vs 372.2 msec ± 77.5, P < .0001) and lower kurtosis of liver T1 (29.1 ± 39.6 vs 43.9 ± 64.9, P = .016) than patients with Child-Pugh class A disease. Prolonged liver T1 (≥462 msec) (hazard ratio [HR], 5.9; 95% confidence interval [CI]: 1.1, 62.8) and an albumin level of less than 3.5 g/dL (HR, 20.7; 95% CI: 3.9, 221.9) were independently associated with the development of hepatic insufficiency. Functional liver volume-to-weight ratio was associated with the development of hepatic decompensation in patients with Child-Pugh class A disease (HR, 0.03; 95% CI: 0.004, 0.23). Conclusion B1 inhomogeneity-corrected volumetric T1 mapping provided information on global liver function and demonstrated functional heterogeneity. In addition, prolonged liver T1 (≥462 msec) was associated with the development of hepatic insufficiency, and functional liver volume-to-weight ratio was negatively related with the development of decompensation in compensated cirrhosis. © RSNA, 2016 Online supplemental material is available for this article.

Acceleration-selective arterial spin labeling for intracranial MR angiography with improved visualization of cortical arteries and suppression of cortical veins.

PURPOSE: A new approach for intracranial MR angiography (MRA) is introduced, using acceleration-selective arterial spin labeling (AccASL). The aim of this study was to investigate the arterial visualization and venous suppression using AccASL. METHODS: Intracranial MRA images obtained by AccASL and time-of-flight (TOF) were compared in seven healthy volunteers and one patient with occlusion of the terminal portion of the left internal carotid artery. The volunteer images were assessed by measuring the contrast-to-noise ratio (CNR) between the middle cerebral artery (MCA) and white matter (WM) and between the confluence of sinuses and WM. Additionally, visualized peripheral arteries were counted and qualitative scoring of the MCA visualization and vein signal contamination was conducted. RESULTS: The CNR at the M4 branch and the number of visualized arteries was significantly higher using AccASL compared with that in TOF (P < 0.05). In the qualitative comparison, the score for artery visualization was higher using AccASL (P < 0.05), while minimizing signal contamination by cortical veins. Additionally, in patient examination, the collateral flow visualization was better with AccASL. CONCLUSION: AccASL enables better efficiency for visualizing peripheral arteries compared with TOF, while suppressing cortical vein signal. Magn Reson Med 77:1996-2004, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Hyperecho PROPELLER-MRI: Application to rapid high-resolution motion-insensitive T2 -weighted black-blood imaging of the carotid arterial vessel wall and plaque.

PURPOSE: To demonstrate the usefulness of hyperecho and PROPELLER (HEP) for carotid arterial vessel wall imaging by using a quantitative comparison with conventional methods. PROPELLER is a motion-insensitive turbo spin-echo (TSE) sequence and has recently been utilized in magnetic resonance (MR) plaque imaging instead of double inversion recovery TSE (DIR-TSE). Wider blade-width, higher k-space density, and an improved blood suppression effect result in better image quality. In this study we introduce a new combination of HEP. MATERIALS AND METHODS: A total of 17 subjects were examined on a 3.0T system. We conducted quantitative comparisons for signal-to-noise ratio (SNR), contrast-to-noise-ratio, and image sharpness among HEP, DIR-TSE, and conventional PROPELLER (c-PROPELLER). Subsequently, images obtained with DIR-TSE, c-PROPELLER, and HEP were visually evaluated using a three-point scale by two board-certified radiologists. RESULTS: HEP showed high SNR similar to c-PROPELLER, good T2 contrast approximating DIR-TSE, and better blood suppression compared with the other two methods (P < 0.05). The image sharpness of HEP (2.55 ± 0.53) was higher than that of DIR-TSE (1.89 ± 0.33) and the absence of ghost or streak artifacts in HEP (2.89 ± 0.33) was better than that in both other methods (2.22 ± 0.83 for DIR-TSE and 2.00 ± 0.50 for c-PROPELLER) (P < 0.05). Furthermore, the degree of blood suppression, particularly in cases of slow or turbulent flow close to the atherosclerotic plaque, was identical for HEP (2.80 ± 0.45) and DIR-TSE (2.80 ± 0.45) but was significantly better than for c-PROPELLER (1.60 ± 0.55) (P < 0.05). CONCLUSION: This study demonstrates the usefulness of HEP in the carotid arteries. HEP can provide higher-resolution T2 -weighted black-blood imaging without flow- and/or motion-related artifacts, compared to conventional techniques. LEVEL OF EVIDENCE: 3 J. Magn. Reson. Imaging 2017;45:515-524.

Usefulness of 3D hybrid profile order technique with 3T magnetic resonance cholangiography: Comparison of image quality and acquisition time.

PURPOSE: To evaluate the image quality and acquisition time of magnetic resonance cholangiopancreatography (MRCP) with and without the 3D hybrid profile order technique. MATERIALS AND METHODS: We studied 32 consecutive patients at 3T. They underwent MRCP with and without the 3D hybrid profile order imaging technique during free breathing and MRCP with the 3D hybrid profile order technique during a single breath-hold. The image acquisition time was 82% shorter with the 3D hybrid profile order technique than without it. The contrast, signal-to-noise-ratio (SNR), and contrast-noise-ratio (CNR) between the common bile duct (CBD) and periductal tissues on 3D-MRCP were evaluated quantitatively. RESULTS: The contrast, SNR, and CNR of the CBD under free breathing was significantly higher with the 3D hybrid profile order technique than without it (P < 0.01). The contrast, SNR, and CNR of the CBD under a single breath-hold was significantly higher with the 3D hybrid profile order technique than without it (P < 0.01). There were no significant differences in the contrast, SNR, and CNR of the CBD between the 3D hybrid profile order with a single breath-hold and with free breathing (P = 0.12, 0.28, 0.28, respectively). CONCLUSION: Using 3T MRI for MRCP with the 3D hybrid profile order sequence yielded significantly improved contrast and CNR with a shorter image acquisition time without sacrificing image quality when compared to imaging without the 3D hybrid profile order sequence. J. Magn. Reson. Imaging 2016;44:1346-1353.

Comparison of multislice breath-hold and 3D respiratory triggered T1 ρ imaging of liver in healthy volunteers and liver cirrhosis patients in 3.0 T MRI.

PURPOSE: To compare visual quality and quantitative measurements of multislice (MS) breath-hold and 3D respiratory-triggered T1 ρ sequences. MATERIALS AND METHODS: T1 ρ scans including MS BLOCK T1 ρ, MS HS8 T1 ρ, and 3D BLOCK T1 ρ were performed on 40 healthy volunteers and 17 liver cirrhosis patients on 3.0T magnetic resonance imaging (MRI). The MS breath-hold methods scanned three slices while the 3D method covered 26 slices. Visual scores of image quality, T1 ρ measurements of the three sequences, and T1 ρ values of healthy volunteers and cirrhosis patients were compared using parametric tests. RESULTS: Average visual scores for volunteers and patients of the three sequences were 3.19 and 2.82 for MS BLOCK T1 ρ; 3.71 and 3.59 for MS HS8 T1 ρ; 3.29 and 3.59 for 3D BLOCK T1 ρ, respectively. Difference of visual scores among the three groups was significant (P < 0.001). Differences in T1 ρ values among the three methods were significant (P < 0.001). Difference of T1 ρ between MS BLOCK T1 ρ and 3D BLOCK T1 ρ was not significant (volunteer: P = 0.82, patient: 0.92) while the difference of T1 ρ between MS BLOCK T1 ρ and MS HS8 T1 ρ, MS HS8 T1 ρ and 3D BLOCK T1 ρ was significant in both volunteers and patients (P < 0.01). Differences of T1 ρ between healthy volunteers and patients were all significant in three T1 ρ sequences (P = 0.04, 0.004, 0.03). CONCLUSION: Of the tested sequences, the image quality of MS HS8 T1 ρ was best, but 3D BLOCK T1 ρ with respiratory triggering should also be considered as an alternative sequence for clinical diagnosis of liver cirrhosis due to its superior coverage. J. MAGN. RESON. IMAGING 2016;44:906-913.

Triexponential function analysis of diffusion-weighted MRI for diagnosing prostate cancer.

BACKGROUND: To evaluate more detailed information noninvasively through on diffusion and perfusion in prostate cancer (PCa) using triexponential analysis of diffusion-weighted imaging (DWI). METHODS: Sixty-three prostate cancer patients underwent preoperative 3.0 Tesla MRI including eight b-values DWI. Triexponential analysis was performed to obtain three diffusion coefficients (Dp , Df , Ds ), as well as fractions (Fp , Ff , Fs ). Each diffusion parameter for cancerous lesions and normal tissues was compared and the relationship between diffusion parameters and Gleason score (GS) was assessed. K(trans) , Ve , and the ratios of intracellular components measured in histopathological specimens were compared with diffusion parameters. RESULTS: Dp was significantly greater for cancerous lesions than normal peripheral zone (PZ) (P < 0.001), whereas Dp in transition zone (TZ) showed no significant difference (P = 0.74, 95% confidence interval (CI) = -4.69-6.48). Ds was significantly smaller for each cancerous lesions in PZ and TZ (P < 0.001, respectively). There was no significant difference in Df between cancerous lesions and normal tissues in PZ and TZ (P = 0.07, 95% CI = -0.29-0.12 and P = 0.53, 95% CI = -3.51-2.29, respectively). D obtained with biexponential analysis were significantly smaller in cancerous lesions than in normal tissue in PZ and TZ (P < 0.001 for both), while D* in PZ and TZ showed no significant difference (P = 0.14, 95% CI = -1.60-0.24 and P = 0.31, 95% CI = -3.43-1.16, respectively). Dp in PZ and TZ showed significant correlation with K(trans) (R = 0.85, P < 0.001; R = 0.81, P < 0.001, respectively), while D(*) in PZ obtained with biexponential analysis showed no such correlation (P = 0.08, 95% CI = -0.14-0.30). Fs was significantly correlated with intracellular space fraction evaluated in histopathological specimens in PZ and TZ cancer (R = 0.41, P < 0.05; R = 0.59, P < 0.001, respectively). Ff and Fs correlated significantly with GS in PZ and TZ cancer (PZ: R = -0.44, P < 0.05; R = 0.37, P < 0.05, TZ: R = -0.59, P < 0.05; R = 0.57, P < 0.05, respectively). CONCLUSION: Triexponential analysis is a noninvasive approach that can provide more detailed information regarding diffusion and perfusion of PCa than biexponential analysis.

T1 ρ Relaxation of the liver: A potential biomarker of liver function.

PURPOSE: To investigate the diagnostic potential of T1 ρ relaxation for assessing liver function, liver fibrosis, or liver necroinflammation in patients with chronic liver disease (CLD). MATERIALS AND METHODS: We obtained T1 ρ maps of the liver for 53 patients with or without CLD. We measured the T1 ρ values of the liver and correlated them with the results of laboratory tests and histological examinations. Pearson's correlation coefficients (r) were calculated between the T1 ρ values and blood serum parameters including the retention rates at 15 minutes after an injection of indocyanine green (ICG-R15). Spearman's rank correlation coefficients were calculated between the T1 ρ values and the scores of liver fibrosis or liver necroinflammation. RESULTS: The T1 ρ values showed significant positive correlations with the serum levels of total bilirubin (r = 0.31, P < 0.05), direct bilirubin (r = 0.32, P < 0.05), and ICG-R15 (r = 0.46, P < 0.05), and significant negative correlations with the serum levels of albumin (r = -0.33, P < 0.05) and γ-glutamyl transpeptidase (r = -0.28, P < 0.05). However, there were no significant correlations between the T1 ρ value and the scores of liver fibrosis (P = 0.95) or liver necroinflammation (P = 0.86). CONCLUSION: T1 ρ relaxation has potential as a biomarker of liver function in patients with CLD. However, it may not be suitable to estimate liver fibrosis or liver necroinflammation.

Perfusion imaging of parotid gland tumours: usefulness of arterial spin labeling for differentiating Warthin's tumours.

OBJECTIVE: To assess prospectively the efficacy of arterial spin labelling (ASL) against conventional and diffusion-weighted (DW) MR imaging for differentiating parotid gland tumours. METHODS: We included 10 pleomorphic adenomas, 12 Warthin's tumours, and nine malignant tumours of the parotid glands. Only tumours larger than 10 mm were included in this study. All parotid gland tumours underwent T1-weighted, T2-weighted, DW, and ASL imaging. Tumour-to-parotid gland signal intensity ratios (SIRs) and apparent diffusion coefficients (ADCs) of solid components were correlated with these pathologies. RESULTS: SIRs on T2-weighted images and ADCs were higher in pleomorphic adenomas than in Warthin's tumours (p < .01) and malignant tumours (p < .01). SIRs on ASL were higher in Warthin's tumours than in pleomorphic adenomas (p < .01) and malignant tumours (p < .05). Az value of SIRs on ASL for differentiating Warthin's tumours from the other pathologies was 0.982. The sensitivity, specificity, and accuracy of SIRs on ASL for the diagnosis of Warthin's tumours at an optimal SIR threshold of over 8.70 were 91.7%, 94.7%, and 93.5%, respectively. CONCLUSIONS: ASL with SIR measurements could non-invasively evaluate tumour blood flow of parotid gland tumours and differentiate Warthin's tumours from pleomorphic adenomas and malignant tumours. KEY POINTS: • ASL non-invasively evaluates tumour blood flow of parotid gland tumours • ASL differentiates Warthin's tumours from pleomorphic adenomas and malignant tumours • ASL cannot differentiate between pleomorphic adenomas and malignant tumours.

Diffusion kurtosis imaging study of prostate cancer: preliminary findings.

PURPOSE: To evaluate the differences in parameters of diffusion kurtosis imaging (DKI) between prostate cancer, benign prostatic hyperplasia (BPH), and benign peripheral zone (PZ). MATERIALS AND METHODS: Twenty-four foci of prostate cancer, 41 BPH nodules (14 stromal and 27 nonstromal hyperplasia), and 20 benign PZ from 20 patients who underwent radical prostatectomy were investigated. Diffusion-weighted imaging (DWI) was performed using 11 b-values (0-1500 s/mm(2) ). DKI model relates DWI signal decay to parameters that reflect non-Gaussian diffusion coefficient (D) and deviations from normal distribution (K). A mixed model analysis of variance and receiver operating characteristic (ROC) analyses were performed to assess the statistical significance of the metrics of DKI and apparent diffusion coefficient (ADC). RESULTS: K was significantly higher in prostate cancer and stromal BPH than in benign PZ (1.19 ± 0.24 and 0.99 ± 0.28 versus 0.63 ± 0.23, P < 0.001 and P < 0.001, respectively). K showed a trend toward higher levels in prostate cancer than in stromal BPH (1.19 ± 0.24 versus 0.99 ± 0.28, P = 0.051). On the ROC analyses, a significant difference in area under the curve was not observed between K and ADC, however, K showed the highest sensitivity among three parameters. CONCLUSION: DKI may contribute to the imaging diagnosis of prostate cancer, especially in the differential diagnosis of prostate cancer and BPH.

[Analysis of accidents for magnetically induced displacement of the large ferromagnetic material in magnetic resonance systems].

To improve magnetic resonance (MR) safety, we surveyed the accidents caused by large ferromagnetic materials brought into MR systems accidentally. We sent a questionnaire to 700 Japanese medical institutions and received 405 valid responses (58%). A total of 97 accidents in 77 institutions were observed and we analyzed them regarding incidental rate, the detail situation and environmental factors. The mean accident rate of each institute was 0.7/100,000 examinations, which was widely distributed (0-25.6/100,000) depending on the institute. In this survey, relatively small institutes with less than 500 beds tend to have these accidents more frequently (p<0.01). The institutes in which daily MR examination counts are more than 10 patients have fewer accidents than those with less than 10 daily examinations. The institutes with 6-10 MR examinations daily have significantly more accidents than that with more than 10 daily MR examinations (p<0.01). The main mental factors of the accidents were considered to be "prejudice" and "carelessness" but some advocate "ignorance." Though we could not find significant reduction in the institutes that have lectures and training for MR safety, we should continue lectures and training for MR safety to reduce accidents due to "ignorance."

T2* relaxometry mapping of the uterine zones.

BACKGROUND: Previous literature demonstrated that the T2* value of the uterine junctional zone was lower than that of peripheral myometrium by using BOLD MR imaging. We expect T2* mapping image may add more information to T2-weighted images of the uterine myometrium. PURPOSE: To evaluate whether T2* mapping software would reproduce the result of previous report, and to apply the software to benign uterine diseases. MATERIAL AND METHODS: Five healthy volunteers and 19 patients clinically suspected of having benign pelvic disease were imaged using a 1.5T MR system. All women were of reproductive age, and all provided informed consent. Sagittal T2* images using a multishot EPI sequence were obtained. T2* values were calculated and color T2* maps reconstructed using a T2* fitting tool. RESULTS: The uterine zones could be identified in all 24 examinations on the T2* maps. In addition, a thin "4th zone" was seen between the endometrium and the JZ (junctional zone) in 19 of 24 examinations. The T2* value of JZ was significantly lower than that of peripheral myometrium (PM) (P < 0.001). No significant difference in the T2* value of the JZ or of PM was noted between normal uterus and uterus with leiomyomas and/or adenomyosis. CONCLUSION: A quantitative T2* map can easily be obtained using the PRIDE software T2* fitting tool, and the software reproduces the result from previous report. T2* value of the junctional zone was lower than that of peripheral myometrium regardless of having benign myometrial diseases.

Identification and further differentiation of subendocardial and transmural myocardial infarction by fast strain-encoded (SENC) magnetic resonance imaging at 3.0 Tesla.

OBJECTIVES: To investigate whether subendocardial and transmural myocardial infarction can be identified and differentiated using the peak circumferential and longitudinal strains measured by fast strain-encoded (SENC). METHODS: Nineteen patients with ischemic heart diseases underwent imaging with fast SENC and late gadolinium enhancement (LGE) MRI at 3 T. Fast SENC measurements were performed in three short-axis slices (basal, mid-ventricular and apical levels) and one long-axis view (four-chamber) to assess peak longitudinal and circumferential systolic strains. RESULTS: All patients showed myocardial infarction with an average of 7 positive LGE segments. A total of 304 segments for longitudinal strains (LS) and 114 segments for circumferential strains (CS) could be analysed. Positive LGE segments showed lower peak CS and LS compared with the no LGE segments (P < 0.0001 for both). Segments with subendocardial infarction showed reduced CS and LS compared with the no LGE segments (P < 0.0001 for both). There was a significant difference in CS between subendocardial and transmural infarct segments (P = 0.03), but no significant difference in LS between them (P = 0.64). CONCLUSIONS: Fast SENC can identify old myocardial infarction and differentiate subendocardial from transmural infarction.

Unenhanced fat fraction ratios obtained by MR and enhanced T2* values with liver-specific MR contrast agents for diagnosis of non-alcoholic steatohepatitis in rats.

BACKGROUND: Non-invasive MR imaging is expected to be used for accurate diagnosis and quantification of non-alcoholic steatohepatitis (NASH), because NASH is a progressive fatty liver disease. New MR techniques, such as fat fraction ratio (FFR) and T2* value measurement, have attracted an increasing attention, because those techniques can measure quantitative parameters of fibrosis, fat and iron deposition in the liver. PURPOSE: To investigate the potential of FFR and T2* value in NASH with pre-enhancement, gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) or super-paramagnetic iron oxide (SPIO)-enhanced MRI. MATERIAL AND METHODS: Twenty-eight rats were divided equally into four groups (one control group and three NASH groups). All rats underwent unenhanced, Gd-EOB-DTPA, and SPIO-enhanced MRI. The T2* value of the liver was measured for each image sequence, and then changes in T2* values before and after each injection were analyzed using Dunnett's test. The reduction rate of T2* value before and 13 min after injection of Gd-EOB-DTPA or SPIO was analyzed using Mann-Whitney's U test. Moreover, FFR of the liver was measured before enhancement, and the relationship between fat fraction and the calculated fat area percentage on a pathological specimen was examined using Spearman's correlation test. RESULTS: On pre-enhancement, FFR and T2* value were 26.0% ± 12.0% and 21.5 ± 4.2 ms for all NASH groups, and 0.9% ± 0.5% and 30.8 ±-5.5 ms for control, respectively. Both FFR and T2* values were significantly different between the NASH and control groups. The reduction rate of T2* value was significantly lower in the NASH groups than in the control group on SPIO-enhanced MRI, though there was no significant difference on Gd-EOB-DTPA-enhanced MRI. FFR was correlated with the calculated fat area percentage for the pathological specimen. CONCLUSION: Pre-enhancement FFR, T2* value measurement and reduction rate of T2* value on SPIO-enhanced MRI may help estimate the progress of liver fat deposition and fibrosis in NASH.

Three Dimensional Ultra-short Echo Time MRI Can Depict Cholesterol Components of Gallstones Bright.

PURPOSE: Non-calcified cholesterol stones that are small in size are hard to be depicted on CT or magnetic resonance cholangiopancreatography. This institutional review board (IRB)-approved retrospective in vitro study aims to characterize contrast behaviors of 3 main components of the gallstones, i.e., cholesterol component (CC), bilirubin calcium component (BC) and CaCO3 (CO) on 3D radial scan with ultrashort TE (UTE) MRI, and to test the capability of depicting CC of gallstones as bright signals as compared to background saline. METHODS: Fourteen representative gallstones from 14 patients, including 15 CC, 6 BC and 4 CO, were enrolled. The gallstones underwent MRI including fat-saturated T1-weighted image (fs-T1WI) and UTE MRI with dual echoes. The contrast-to-noise ratio (CNR) and the chemical analysis for the 25 portions of the stones were compared. RESULTS: BC was bright on fs-T1WI, which did not change dramatically on UTE MRI and the signal did not remain on UTE subtraction image between dual echoes. Whereas the CC was negative or faintly positive signal on fs-T1WI, bright signal on UTE MRI and the contrast remained even higher on the UTE subtraction, which reflected their short T2 values. Median CNRs and standard errors of the segments on each imaging were as follows: on fs-T1WI, -10.2 ± 4.2 for CC, 149.7 ± 27.6 for BC and 37.9 ± 14.3 for CO; on UTE MRI first echo, 16.7 ± 3.3 for CC, 74.9 ± 21.3 for BC and 17.7 ± 8.4 for CO; on UTE subtraction image, 30.2 ±2.0 for CC, -11.2 ± 5.4 for BC and 17.8 ± 10.7 for CO. Linear correlations between CNRs and cholesterol concentrations were observed on fs-T1WI with r = -0.885, (P < 0.0001), UTE MRI first echo r = -0.524 (P = 0.0072) and UTE subtraction with r = 0.598 (P = 0.0016). CONCLUSION: UTE MRI and UTE subtraction can depict CC bright.

Hepatocyte fraction: correlation with noninvasive liver functional biomarkers.

PURPOSE: To evaluate the correlation between HeF obtained from gadoxetic acid-enhanced MR imaging and clinical biomarkers for the assessment of liver function. METHODS: This prospective study was approved by our Institutional Review Board, and written informed consent was obtained from the patients. We recruited 48 patients carrying a known or suspected liver disease to undergo gadoxetic acid-enhanced MR imaging. The new model of the HeF was calculated from ΔR1 values of the liver and spleen. The HeF, quantitative liver-to-spleen contrast ratio (Q-LSC), and ΔT1 value (the reduction rate of the T1 value between the pre- and post-contrast images) were compared with the Child-Pugh and end-stage liver disease (MELD) scores. RESULTS: Among 48 patients, 40 were in Child-Pugh class A and 8 were in class B. The median HeF (P = 0.0001), Q-LSC (P = 0.015), and ΔT1 value (P = 0.0023) in patients in Child-Pugh class A were significantly higher than those in class B. The sensitivities, specificities, and area under the receiver-operating-characteristic curves for differentiating Child-Pugh class A and B were 95.0%, 87.5%, and 0.93 in the HeF; 77.5%, 75.0%, and 0.78 in the Q-LSC; and 57.5%, 100.0%, and 0.84 in the ΔT1 value, respectively. The HeF was significantly correlated with Child-Pugh (r = - 0.58, P < 0.0001) and MELD score (r = - 0.57, P < 0.0001). CONCLUSIONS: The HeF was well correlated with Child-Pugh and MELD score and could be a new biomarker to assess liver function.