Diffusion Kurtosis MR Imaging of Invasive Breast Cancer: Correlations With Prognostic Factors and Molecular Subtypes.

BACKGROUND: The associations between diffusion kurtosis imaging (DKI)-derived parameters and clinical prognostic factors of breast cancer have not been fully evaluated; this knowledge may have implications for outcome prediction and treatment strategies. PURPOSE: To determine associations between quantitative diffusion parameters derived from DKI and diffusion-weighted imaging (DWI) and the prognostic factors and molecular subtypes of breast cancer. STUDY TYPE: Retrospective. POPULATION: A total of 383 women (mean age, 53.8 years; range, 31-82 years) with breast cancer who underwent preoperative breast MRI including DKI and DWI. FIELD STRENGTH/SEQUENCE: A 3.0 T; DKI using a spin-echo echo-planar imaging (EPI) sequence (b values: 200, 500, 1000, 1500, and 2000 sec/mm2 ), DWI using a readout-segmented EPI sequence (b values: 0 and 1000 sec/mm2 ) and dynamic contrast-enhanced breast MRI. ASSESSMENT: Two radiologists (J.Y.K. and H.S.K. with 9 years and 1 year of experience in MRI, respectively) independently measured kurtosis, diffusivity, and apparent diffusion coefficient (ADC) values of breast cancer by manually placing a regions of interest within the lesion. Diffusion measures were compared according to nodal status, grade, and molecular subtypes. STATISTICAL TESTS: Kruskal-Wallis test, Mann-Whitney U test with Bonferroni correction, receiver operating characteristic (ROC) analysis, and multivariate logistic regression analysis. (Statistical significance level of P < 0.05). RESULTS: All diffusion measures showed significant differences according to axillary nodal status and histological grade. Kurtosis showed significant differences among molecular subtypes. The luminal subtype (median 1.163) showed a higher kurtosis value compared to the HER2-positive (median 0.962) or triple-negative subtypes (median 1.072). ROC analysis for differentiating HER2-positive from luminal subtypes revealed that kurtosis yielded the highest area under the curve of 0.781. In multivariate analyses, kurtosis remained a significant factor associated with differentiation between HER2-positive and luminal (odds ratio [OR] = 0.993), triple-negative and luminal (OR = 0.995), and HER2-positive and triple-negative subtypes (OR = 0.994). DATA CONCLUSION: Quantitative diffusion parameters derived from DKI and DWI are associated with prognostic factors for breast cancer. Moreover, DKI-derived kurtosis can help distinguish between the molecular subtypes of breast cancer. EVIDENCE LEVEL: 4 TECHNICAL EFFICACY: 3.

Simultaneous evaluation of perfusion and morphology using GRASP MRI in hepatic fibrosis.

OBJECTIVES: To determine if golden-angle radial sparse parallel (GRASP) dynamic contrast-enhanced (DCE)-MRI allows simultaneous evaluation of perfusion and morphology in liver fibrosis. METHODS: Participants who were scheduled for liver biopsy or resection were enrolled (NCT02480972). Images were reconstructed at 12-s temporal resolution for morphologic assessment and at 3.3-s temporal resolution for quantitative evaluation. The image quality of the morphologic images was assessed on a four-point scale, and the Liver Imaging Reporting and Data System score was recorded for hepatic observations. Comparisons were made between quantitative parameters of DCE-MRI for the different fibrosis stages, and for hepatocellular carcinoma (HCCs) with different LR features. RESULTS: DCE-MRI of 64 participants (male = 48) were analyzed. The overall image quality consistently stood at 3.5 ± 0.4 to 3.7 ± 0.4 throughout the exam. Portal blood flow significantly decreased in participants with F2-F3 (n = 18, 175 ± 110 mL/100 mL/min) and F4 (n = 12, 98 ± 47 mL/100 mL/min) compared with those in participants with F0-F1 (n = 34, 283 ± 178 mL/100 mL/min, p < 0.05 for all). In participants with F4, the arterial fraction and extracellular volume were significantly higher than those in participants with F0-F1 and F2-F3 (p < 0.05). Compared with HCCs showing non-LR-M features (n = 16), HCCs with LR-M (n = 5) had a significantly prolonged mean transit time and lower arterial blood flow (p < 0.05). CONCLUSIONS: Liver MRI using GRASP obtains both sufficient spatial resolution for confident diagnosis and high temporal resolution for pharmacokinetic modeling. Significant differences were found between the MRI-derived portal blood flow at different hepatic fibrosis stages. KEY POINTS: A single MRI examination is able to provide both images with sufficient spatial resolution for anatomic evaluation and those with high temporal resolution for pharmacokinetic modeling. Portal blood flow was significantly lower in clinically significant hepatic fibrosis and mean transit time and extracellular volume increased in cirrhosis, compared with those in no or mild hepatic fibrosis. HCCs with different LR features showed different quantitative parameters of DCE-MRI: longer mean transit time and lower arterial flow were observed in HCCs with LR-M features.

Contact Angle Relaxation on Amorphous, Mixed-Phase (Anatase + Rutile), and Anatase TiO2 Films and Its Mechanism.

TiO2 films generally undergo contact angle relaxation in the dark. It has been suggested that carbon contamination and the loss of surface OH generated by UV may be the major causes. However, the mechanisms for the long-lasting hydrophilicity have not been fully understood. Here, we studied contact angle relaxation of amorphous, mixed-phase, and anatase, and a new mechanism is proposed. After UV exposure and oxygen plasma treatment, the films' relaxation was observed over short-term (1 day) and long-term (>30 days) scales with XPS analysis using two quantitative parameters: relative amount and binding energy (B.E.) shifting. One day after plasma treatment, we observed that the donor-acceptor complex (DAC) and Ti-OH peaks of anatase shifted toward lower B.E., while the other films showed no shift or positive B.E. shifting. Interestingly, the relaxation of the amorphous and mixed-phase TiO2 occurred over time despite the large number of total OH groups (IOH/Ibulk > 75%) and DAC (IDAC/Ibulk > 110%), and only the anatase film showed superhydrophilicity (∼10°) for 90 days. Also, the B.E. of all OH peaks increased over time, indicating that polarizable hydroxyls relaxed in the dark. Although the greater binding strength of Ti-OH and DAC on the anatase surface maintains long-lasting hydrophilicity, the loss of polarizable OH causes relaxation on the less-reactive TiO2 films. Carbon contamination can also contribute to the relaxation over time. Taken together, we conclude that the surface energy, polarizable OH, and contaminants are the major factors affecting relaxation; this study gives a full picture of the mechanism integrated over some of the previously reported models.

Ultrafast Dynamic Contrast-Enhanced MRI Using Compressed Sensing: Associations of Early Kinetic Parameters With Prognostic Factors of Breast Cancer.

OBJECTIVE. The purpose of this study was to investigate whether early kinetic parameters derived from ultrafast dynamic contrast-enhanced MRI (DCE-MRI) using compressed sensing are associated with prognostic factors for breast cancer. MATERIALS AND METHODS. We evaluated 201 consecutive women (mean age, 54.6 years) with breast cancer (168 invasive, 33 ductal carcinoma in situ) who underwent both ultrafast DCE-MRI using compressed sensing (temporal resolution, 4.7 seconds; spatial resolution, 0.8 × 1.1 × 0.9 mm) and surgery between 2018 and 2019. Early kinetic parameters (time to enhancement [TTE] and maximum slope [MS]) were measured in breast lesions by two radiologists using a software program and were correlated with histopathologic prognostic factors. The Mann-Whitney U test and linear regression analysis were used. RESULTS. The median TTE and MS values for breast cancer were 11.9 seconds and 7.7%/s, respectively. The median MS was significantly larger in invasive cancer lesions than in ductal carcinoma in situ lesions (8.4%/s vs 4.7%/s, p < .001). In women with invasive cancer, multivariate linear regression analyses showed that a larger tumor size (> 2 cm) (p = .048) and estrogen receptor-negative status (p < .001) were significantly associated with a shorter TTE. A higher histologic grade (grade 3) (p = .01) was significantly associated with a larger MS. We observed excellent interobserver agreement between two readers in the measurements of TTE and MS (intraclass correlation coefficients, 0.943 and 0.890, respectively). CONCLUSION. Ultrafast MRI-derived early enhancement parameters, such as TTE and MS, are associated with histopathologic prognostic factors in women with breast cancer.

Diffusion-weighted MRI of estrogen receptor-positive, HER2-negative, node-negative breast cancer: association between intratumoral heterogeneity and recurrence risk.

OBJECTIVES: To investigate possible associations between quantitative apparent diffusion coefficient (ADC) metrics derived from whole-lesion histogram analysis and breast cancer recurrence risk in women with estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative, node-negative breast cancer who underwent the Oncotype DX assay. METHODS: This retrospective study was conducted on 105 women (median age, 48 years) with ER-positive, HER2-negative, node-negative breast cancer who underwent the Oncotype DX test and preoperative diffusion-weighted imaging (DWI). Histogram analysis of pixel-based ADC data of whole tumors was performed, and various ADC histogram parameters (mean, 5th, 25th, 50th, 75th, and 95th percentiles of ADCs) were extracted. The ADC difference value (defined as the difference between the 5th and 95th percentiles of ADCs) was calculated to assess intratumoral heterogeneity. Associations between quantitative ADC metrics and the recurrence risk, stratified using the Oncotype DX recurrence score (RS), were evaluated. RESULTS: Whole-lesion histogram analysis showed that the ADC difference value was different between the low-risk recurrence (RS < 18) and the non-low-risk recurrence (RS ≥ 18; intermediate to high risk of recurrence) groups (0.600 × 10-3 mm2/s vs. 0.746 × 10-3 mm2/s, p < 0.001). Multivariate regression analysis demonstrated that a lower ADC difference value (< 0.559 × 10-3 mm2/s; odds ratio [OR] = 5.998; p = 0.007) and a small tumor size (≤ 2 cm; OR = 3.866; p = 0.012) were associated with a low risk of recurrence after adjusting for clinicopathological factors. CONCLUSIONS: The ADC difference value derived from whole-lesion histogram analysis might serve as a quantitative DWI biomarker of the recurrence risk in women with ER-positive, HER2-negative, node-negative invasive breast cancer. KEY POINTS: • A lower ADC difference value and a small tumor size were associated with a low risk of recurrence of breast cancer. • The ADC difference value could be a quantitative marker for intratumoral heterogeneity. • Whole-lesion histogram analysis of the ADC could be helpful for discriminating the low-risk from non-low-risk recurrence groups.

Diffusion-weighted imaging: Apparent diffusion coefficient histogram analysis for detecting pathologic complete response to chemoradiotherapy in locally advanced rectal cancer.

PURPOSE: To investigate the usefulness of apparent diffusion coefficient (ADC) values derived from histogram analysis of the whole rectal cancer as a quantitative parameter to evaluate pathologic complete response (pCR) on preoperative magnetic resonance imaging (MRI). MATERIALS AND METHODS: We enrolled a total of 86 consecutive patients who had undergone surgery for rectal cancer after neoadjuvant chemoradiotherapy (CRT) at our institution between July 2012 and November 2014. Two radiologists who were blinded to the final pathological results reviewed post-CRT MRI to evaluate tumor stage. Quantitative image analysis was performed using T2 -weighted and diffusion-weighted images independently by two radiologists using dedicated software that performed histogram analysis to assess the distribution of ADC in the whole tumor. RESULTS: After surgery, 16 patients were confirmed to have achieved pCR (18.6%). All parameters from pre- and post-CRT ADC histogram showed good or excellent agreement between two readers. The minimum, 10th, 25th, 50th, and 75th percentile and mean ADC from post-CRT ADC histogram were significantly higher in the pCR group than in the non-pCR group for both readers. The 25th percentile value from ADC histogram in post-CRT MRI had the best diagnostic performance for detecting pCR, with an area under the receiver operating characteristic curve of 0.796. CONCLUSION: Low percentile values derived from the ADC histogram analysis of rectal cancer on MRI after CRT showed a significant difference between pCR and non-pCR groups, demonstrating the utility of the ADC value as a quantitative and objective marker to evaluate complete pathologic response to preoperative CRT in rectal cancer. J. Magn. Reson. Imaging 2016;44:212-220.

Correlation of dynamic contrast-enhanced MRI perfusion parameters with angiogenesis and biologic aggressiveness of rectal cancer: Preliminary results.

PURPOSE: To investigate whether quantitative parameters derived from dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) are correlated with angiogenesis and biologic aggressiveness of rectal cancer. MATERIALS AND METHODS: A total of 46 patients with rectal cancer underwent DCE-MRI. Using a two-compartmental model, quantitative parameters (K(trans) , kep , ve , and iAUC) were calculated from the whole-transverse region of interest (ROI) and high K(trans) area ROI of entire tumors. Histological specimens were analyzed for tumor size; T/N stage; lymphatic, vascular, perineural invasion; expression of epidermal growth factor receptor (EGFR); and KRAS gene mutations. Tumor angiogenesis was evaluated based on the microvessel density (MVD) and the expression level of the vascular endothelial growth factor. Correlations of the DCE-MRI parameters with histological markers and angiogenesis were determined using Student's t-test and analysis of variance (ANOVA). RESULTS: The mean kep from high K(trans) area ROIs showed a significantly positive correlation with MVD (P = 0.030, r = 0.514, R(2) = 0.264). The mean kep from the whole-transverse ROIs showed a significant inverse correlation with T stage (T1 vs. T2-4, P = 0.021). EGFR-positive cancer displayed higher mean K(trans) (P = 0.045) and kep (P = 0.038) than EGFR-negative cancer in whole-transverse ROIs. CONCLUSION: These preliminary results suggest that the determination of kep of high K(trans) area permits the noninvasive estimation of tumor angiogenesis in rectal cancer and that DCE-MRI parameters can be used as imaging biomarkers to predict the biologic aggressiveness of the tumor and patient prognosis.

Risk Factor Analysis of Cryopreserved Autologous Bone Flap Resorption in Adult Patients Undergoing Cranioplasty with Volumetry Measurement Using Conventional Statistics and Machine-Learning Technique.

OBJECTIVE: Decompressive craniectomy (DC) with duroplasty is one of the common surgical treatments for life-threatening increased intracranial pressure (ICP). Once ICP is controlled, cranioplasty (CP) with reinsertion of the cryopreserved autologous bone flap or a synthetic implant is considered for protection and esthetics. Although with the risk of autologous bone flap resorption (BFR), cryopreserved autologous bone flap for CP is one of the important material due to its cost effectiveness. In this article, we performed conventional statistical analysis and the machine learning technique understand the risk factors for BFR. METHODS: Patients aged >18 years who underwent autologous bone CP between January 2015 and December 2021 were reviewed. Demographic data, medical records, and volumetric measurements of the autologous bone flap volume from 94 patients were collected. BFR was defined with absolute quantitative method (BFR-A) and relative quantitative method (BFR%). Conventional statistical analysis and random forest with hyper-ensemble approach (RF with HEA) was performed. And overlapped partial dependence plots (PDP) were generated. RESULTS: Conventional statistical analysis showed that only the initial autologous bone flap volume was statistically significant on BFR-A. RF with HEA showed that the initial autologous bone flap volume, interval between DC and CP, and bone quality were the factors with most contribution to BFR-A, while, trauma, bone quality, and initial autologous bone flap volume were the factors with most contribution to BFR%. Overlapped PDPs of the initial autologous bone flap volume on the BRF-A crossed at approximately 60 mL, and a relatively clear separation was found between the non-BFR and BFR groups. Therefore, the initial autologous bone flap of over 60 mL could be a possible risk factor for BFR. CONCLUSION: From the present study, BFR in patients who underwent CP with autologous bone flap might be inevitable. However, the degree of BFR may differ from one to another. Therefore, considering artificial bone flaps as implants for patients with large DC could be reasonable. Still, the risk factors for BFR are not clearly understood. Therefore, chronological analysis and pathophysiologic studies are needed.

Prostate gland volume estimation: anteroposterior diameters measured on axial versus sagittal ultrasonography and magnetic resonance images.

PURPOSE: The aim of this study was to evaluate the accuracy of prostate volume estimates calculated from the ellipsoid formula using the anteroposterior (AP) diameter measured on axial and sagittal images obtained through ultrasonography (US) and magnetic resonance imaging (MRI). METHODS: This retrospective study included 456 patients with transrectal US and MRI from two university hospitals. Two radiologists independently measured the prostate gland diameters on US and MRI: AP diameters on axial and sagittal images, transverse, and longitudinal diameters on midsagittal images. The volume estimates, volumeax and volumesag, were calculated from the ellipsoid formula by using the AP diameter on axial and sagittal images, respectively. The prostate volume extracted from MRI-based whole-gland segmentation was considered the gold standard. The intraclass correlation coefficient (ICC) was used to evaluate the inter-method agreement between volumeax and volumesag, and agreement with the gold standard. The Wilcoxon signedrank test was used to analyze the differences between the volume estimates and the gold standard. RESULTS: The prostate gland volume estimates showed excellent inter-method agreement, and excellent agreement with the gold standard (ICCs >0.9). Compared with the gold standard, the volume estimates were significantly larger on MRI and significantly smaller on US (P<0.001). The volume difference (segmented volume-volume estimate) was greater in patients with larger prostate glands, especially on US. CONCLUSION: Volumeax and volumesag showed excellent inter-method agreement and excellent agreement with the gold standard on both US and MRI. However, prostate volume was overestimated on MRI and underestimated on US.

Comparison of the Effects of Hepatic Steatosis on Monoexponential DWI, Intravoxel Incoherent Motion Diffusion-weighted Imaging and Diffusion Kurtosis Imaging.

RATIONALE AND OBJECTIVES: Diffusion-weighted imaging (DWI) techniques have drawn attention for their capability of staging hepatic fibrosis. However, the diagnostic performance of DWI for hepatic fibrosis might be affected by hepatic steatosis because hepatic steatosis and fibrosis may have a similar effect on diffusion/perfusion parameters. Therefore, the purpose of our study is to investigate the effect of hepatic steatosis on DWI parameters. MATERIALS AND METHODS: 51 patients with MR elastography liver stiffness values below 3.45kPa underwent DWI with multiple b-values and a multi-echo Dixon sequence for fat quantification. Correlation analysis was conducted between fat fraction and DWI parameters, and DWI parameters were compared between steatosis and non-steatosis groups. RESULTS: Significant negative correlation was observed between fat fraction and apparent diffusion coefficient (ADC) (r = -0.62, p <0.001), pure molecular diffusion (D) (r = -0.62, p <0.001), corrected ADC (Dapp) (r = -0.36, p = 0.01) and a positive correlation with mean kurtosis (Kapp) (r = 0.53, p <0.001). The results of the comparison of DWI parameters were that ADC, D and Dapp were statistically lower in the steatosis group (p < 0.001, p < 0.001 and p = 0.026, respectively) and Kapp was significantly higher in the steatosis group (p <0.001) compared to the non-steatosis group. However, perfusion-related parameters (D* and f) did not show any statistical significance. CONCLUSION: DWI parameters except for perfusion-related parameters (D* and f) are affected by changes in hepatic steatosis. Thus, hepatic steatosis may be considered as a possible confounding factor in DWI-based assessment of liver fibrosis.

Image quality and diagnostic value of diffusion-weighted breast magnetic resonance imaging: Comparison of acquired and computed images.

PURPOSE: To compare the image quality of acquired diffusion-weighted imaging (DWI) and computed DWI and evaluate the lesion detectability and likelihood of malignancy in these datasets. MATERIALS AND METHODS: This prospective study was approved by our institutional review board. A total of 29 women (mean age, 43.5 years) underwent DWI between August 2018 and April 2019 for 32 breast cancers and 16 benign breast lesions. Three radiologists independently reviewed the acquired DWI with b-values of 1000 and 2000 s/mm2 (A-b1000 and A-b2000) and the computed DWI with a b-value of 2000 s/mm2 (C-b2000). Image quality was scored and compared between the three DWI datasets. Lesion detectability was recorded, and the lesion's likelihood for malignancy was scored using a five-point scale. RESULTS: The A-b1000 images were superior to the A-b2000 and C-b2000 images in chest distinction, fat suppression, and overall image quality. The A-b2000 and C-b2000 images showed comparable scores for all image quality parameters. C-b2000 showed the highest values for lesion detection among all readers, although there was no statistical difference in sensitivity, specificity, positive predictive value, negative predictive value, and accuracy between the DWI datasets. The malignancy scores of the DWI images were not significantly different among the three readers. CONCLUSIONS: A-b1000 DWI is suitable for breast lesion evaluations, considering its better image quality and comparable diagnostic values compared to that of A-b2000 and C-b2000 images. The additional use of computed high b-value DWI may have the potential to increase the detectability of breast masses.

Detection and PI-RADS classification of focal lesions in prostate MRI: Performance comparison between a deep learning-based algorithm (DLA) and radiologists with various levels of experience.

PURPOSE: To compare the performance of lesion detection and Prostate Imaging-Reporting and Data System (PI-RADS) classification between a deep learning-based algorithm (DLA), clinical reports and radiologists with different levels of experience in prostate MRI. METHODS: This retrospective study included 121 patients who underwent prebiopsy MRI and prostate biopsy. More than five radiologists (Reader groups 1, 2: residents; Readers 3, 4: less-experienced radiologists; Reader 5: expert) independently reviewed biparametric MRI (bpMRI). The DLA results were obtained using bpMRI. The reference standard was based on pathologic reports. The diagnostic performance of the PI-RADS classification of DLA, clinical reports, and radiologists was analyzed using AUROC. Dichotomous analysis (PI-RADS cutoff value ≥ 3 or 4) was performed, and the sensitivities and specificities were compared using McNemar's test. RESULTS: Clinically significant cancer [CSC, Gleason score ≥ 7] was confirmed in 43 patients (35.5%). The AUROC of the DLA (0.828) for diagnosing CSC was significantly higher than that of Reader 1 (AUROC, 0.706; p = 0.011), significantly lower than that of Reader 5 (AUROC, 0.914; p = 0.013), and similar to clinical reports and other readers (p = 0.060-0.661). The sensitivity of DLA (76.7%) was comparable to those of all readers and the clinical reports at a PI-RADS cutoff value ≥ 4. The specificity of the DLA (85.9%) was significantly higher than those of clinical reports and Readers 2-3 and comparable to all others at a PI-RADS cutoff value ≥ 4. CONCLUSIONS: The DLA showed moderate diagnostic performance at a level between those of residents and an expert in detecting and classifying according to PI-RADS. The performance of DLA was similar to that of clinical reports from various radiologists in clinical practice.

Clinical Feasibility of Abbreviated Magnetic Resonance With Breath-Hold 3-Dimensional Magnetic Resonance Cholangiopancreatography for Surveillance of Pancreatic Intraductal Papillary Mucinous Neoplasm.

OBJECTIVES: To determine the clinical feasibility of abbreviated magnetic resonance image (MRI) using breath-hold 3-dimensional magnetic resonance cholangiopancreatography (3D-MRCP) (aMRI-BH) for pancreatic intraductal papillary mucinous neoplasm (IPMN) surveillance. MATERIALS AND METHODS: In this retrospective study, 123 patients with 158 pancreatic IPMNs (pathologically proven [n = 73] and typical image feature with ≥2-year stability [n = 85]) who underwent conventional MRI (cMRI) consisting of contrast-enhanced pancreatobiliary MRI with conventional and BH-3D-MRCP were included. Two readers independently evaluated aMRI-BH protocols consisting of heavily T2-weighted, precontrast T1-weighted, and BH-3D-MRCP sequences. The diagnostic performance of aMRI-BH for detecting malignant IPMNs was assessed using the following criteria: category 3, presence of mural nodule 5 mm or bigger and/or main pancreatic duct (MPD) 10 mm or bigger; category 2, more than one of the following: cyst size 30 mm or greater, mural nodule smaller than 5 mm, thickened cyst walls, MPD of 5 to 9 mm, lymphadenopathy, and an abrupt MPD caliber change with distal atrophy; and category 1, none of the above. Categories 2 or 3 were considered positive results of surveillance. Interreader agreement of image features by intraclass correlation and κ statistics were analyzed. RESULTS: The total acquisition times of cMRI and aMRI-BH were 32.7 ± 8 and 5.5 ± 2.1 minutes, respectively (P < 0.01). Among 158 IPMNs, 33 lesions were malignant. The aMRI-BH presented a sensitivity of 100% and a negative predictive value of 100% for evaluating malignant IPMNs in both readers, with substantial interreader agreements (intraclass correlation or к values, range: 0.73-0.93 for cMRI and 0.57-0.94 for aMRI-BH) in significant imaging features based on revised Fukuoka guidelines, except for thickened cyst walls and lymphadenopathy (к values: 0.10 and 1.00 for cMRI and 0.13 and 0.49 for aMRI-BH, respectively). CONCLUSIONS: The aMRI-BH provided high sensitivity and negative predictive value to evaluate malignant IPMNs by using predetermined criteria, and aMRI-BH might be a potential tool for pancreatic IPMN surveillance with significantly lower acquisition time.

Clinical value of pointwise encoding time reduction with radial acquisition (PETRA) MR sequence in assessing internal derangement of knee.

PURPOSE: The purpose was to evaluate the clinical value of PETRA sequence for the diagnosis of internal derangement of the knee. MATERIALS AND METHODS: The major structures of the knee in 34 patients were evaluated and compared among conventional MRI findings, PETRA images, and arthroscopic findings. RESULTS: The specificities of PETRA with 2D FSE sequence were higher for meniscal lesions than those obtained when using 2D FSE alone. CONCLUSION: Using PETRA images along with conventional 2D FSE images can increase the accuracy of assessing internal derangements of the knee and, specifically, meniscal lesions.

Validation of intimate correlation between visceral fat and hepatic steatosis: Quantitative measurement techniques using CT for area of fat and MR for hepatic steatosis.

BACKGROUND & AIM: The relationship between obesity and hepatic steatosis is well known, and there are many methods to measure obesity and severity of hepatic steatosis. Because of advances in radiologic techniques, the areas of certain body components can be measured on computed tomography (CT) while the severity of hepatic steatosis can be measured by magnetic resonance spectroscopy (MRS) with high accuracy. The aim of this study is to investigate the relationship between degree of fatty infiltration of the liver measured by MRS and body composition measured from CT images. MATERIALS AND METHODS: We evaluated 95 potential liver donors who underwent abdomen CT and liver MRI (including MRS) between February 2014 and September 2015 in a tertiary university hospital. Body composition analysis was performed on CT images using commercial software. The areas of subcutaneous fat, visceral fat and abdominal circumference were measured automatically and the area of muscle was measured semi-automatically. The degree of hepatic steatosis was measured by MRS. RESULTS: The degree of hepatic steatosis showed a significant correlation with total fat area, visceral fat area, subcutaneous fat area, muscle area, abdominal circumference, BMI, and ratio of visceral fat to total fat. The strongest correlation was between hepatic steatosis and the area of visceral fat in all subjects (r=0.569). Multivariate regression analysis showed that male gender and visceral fat area were significantly associated with hepatic steatosis (P = 0.031, <0.001, respectively). CONCLUSIONS: The area of visceral fat has the most intimate correlation to the severity of hepatic steatosis among all significantly correlated parameters associated with body habitus. Accurate and quantitative body composition measurement and degree of hepatic steatosis can be noninvasively performed using advanced radiological techniques.

Differentiation of multiple myeloma and metastases: Use of axial diffusion-weighted MR imaging in addition to standard MR imaging at 3T.

BACKGROUND: Metastasis and multiple myeloma are common malignant bone marrow lesions which may be difficult to distinguish because of similar imaging findings. The purpose of this study was to determine the value of adding diffusion-weighted imaging (DWI) to standard MR imaging to differentiate multiple myeloma from metastasis. METHODS: 25 patients with metastasis and 18 patients with multiple myeloma underwent 3T MR imaging with DWI (b = 0, 800 s/mm2) were enrolled. They all had pathologically confirmed bone lesions and were in a treatment naïve state. Two readers who were blind of final diagnosis measured the average ADC (ADCav) and minimum ADC (ADCmin) on the DWI. They then estimated the diagnosis, based on the standard MR imaging and measured ADC values. Another reader performed histogram analysis on the whole tumor volume and obtained mean ADC (ADCvol), standard deviation (SDvol), skewness, and kurtosis. Comparison of the obtained values from DWI was performed by the t-test or Mann-Whitney U test. The receiver operating characteristic (ROC) curve with areas under the curve (AUC) was used to obtain the cut off values and to evaluate the diagnostic performance of the two readers. RESULTS: ADCav, ADCmin, and ADCvol of multiple myeloma were significantly lower than those of metastasis: ADCav, 752 µm2/sec versus 1081 µm2/sec; ADCmin, 704 µm2/sec vs 835 µm2/sec; ADCvol 761 µm2/sec vs 1184 µm2/sec (p < .001). In histogram analysis, ADC values of multiple myeloma showed narrow distribution than metastasis: SDvol, 144 vs 257 (p < .001). Areas under the receiver operating characteristic curve was significantly higher with additive DWI than standard MR alone: 0.762 vs 0.953; 0.706 vs 0.950 (p < .05) for two readers. CONCLUSIONS: This study suggested that the addition of axial DWI to standard MR imaging can be helpful to diagnose multiple myeloma from metastasis at 3T.

Evaluation of Transient Motion During Gadoxetic Acid-Enhanced Multiphasic Liver Magnetic Resonance Imaging Using Free-Breathing Golden-Angle Radial Sparse Parallel Magnetic Resonance Imaging.

OBJECTIVES: The aims of this study were to observe the pattern of transient motion after gadoxetic acid administration including incidence, onset, and duration, and to evaluate the clinical feasibility of free-breathing gadoxetic acid-enhanced liver magnetic resonance imaging using golden-angle radial sparse parallel (GRASP) imaging with respiratory gating. MATERIALS AND METHODS: In this institutional review board-approved prospective study, 59 patients who provided informed consents were analyzed. Free-breathing dynamic T1-weighted images (T1WIs) were obtained using GRASP at 3 T after a standard dose of gadoxetic acid (0.025 mmol/kg) administration at a rate of 1 mL/s, and development of transient motion was monitored, which is defined as a distinctive respiratory frequency alteration of the self-gating MR signals. Early arterial, late arterial, and portal venous phases retrospectively reconstructed with and without respiratory gating and with different temporal resolutions (nongated 13.3-second, gated 13.3-second, gated 6-second T1WI) were evaluated for image quality and motion artifacts. Diagnostic performance in detecting focal liver lesions was compared among the 3 data sets. RESULTS: Transient motion (mean duration, 21.5 ± 13.0 seconds) was observed in 40.0% (23/59) of patients, 73.9% (17/23) of which developed within 15 seconds after gadoxetic acid administration. On late arterial phase, motion artifacts were significantly reduced on gated 13.3-second and 6-second T1WI (3.64 ± 0.34, 3.61 ± 0.36, respectively), compared with nongated 13.3-second T1WI (3.12 ± 0.51, P < 0.0001). Overall, image quality was the highest on gated 13.3-second T1WI (3.76 ± 0.39) followed by gated 6-second and nongated 13.3-second T1WI (3.39 ± 0.55, 2.57 ± 0.57, P < 0.0001). Only gated 6-second T1WI showed significantly higher detection performance than nongated 13.3-second T1WI (figure of merit, 0.69 [0.63-0.76]) vs 0.60 [0.56-0.65], P = 0.004). CONCLUSIONS: Transient motion developed in 40% (23/59) of patients shortly after gadoxetic acid administration, and gated free-breathing T1WI using GRASP was able to consistently provide acceptable arterial phase imaging in patients who exhibited transient motion.

Clinical Feasibility of 3-Dimensional Magnetic Resonance Cholangiopancreatography Using Compressed Sensing: Comparison of Image Quality and Diagnostic Performance.

OBJECTIVE: The aim of this study was to evaluate the clinical feasibility of fast 3-dimensional (3D) magnetic resonance cholangiopancreatography (MRCP) using compressed sensing (CS) in comparison with conventional navigator-triggered 3D-MRCP. MATERIALS AND METHODS: This retrospective study was approved by our institutional review board, and the requirement of informed consent was waived. A total of 84 patients (male-to-female ratio, 41:43; mean age, 47.3 ± 18.8 years) who underwent conventional 3D navigator-triggered T2-weighted MRCP using sampling perfection with application optimized contrasts (SPACE) and fast 3D MRCP using SPACE with high undersampling combined with CS reconstruction (CS SPACE; CS-MRCP) on a 3 T scanner were included. Among them, 28 patients additionally underwent 3D breath-hold CS-MRCP (BH-CS-MRCP) with 5.7% k-space sampling. Three board-certified radiologists then independently reviewed the examinations for bile duct and pancreatic duct visualization and overall image quality on a 5-point scale, and image sharpness and background suppression on a 4-point scale, with the higher score indicating better image quality. In addition, diagnostic performance for the detection of anatomic variation and diseases of the bile duct, and pancreatic disease were assessed on a per-patient basis in the subgroup of 28 patients who underwent conventional MRCP, CS-MRCP, and BH-CS-MRCP in the same manner. RESULTS: Mean acquisition times of conventional MRCP, CS-MRCP, and BH-CS-MRCP were 7 minutes (419.7 seconds), 3 minutes 47 seconds (227.0 seconds), and 16 seconds, respectively (P < 0.0001, in all comparisons). In all patients, CS-MRCP showed better image sharpness (3.54 ± 0.60 vs 3.37 ± 0.75, P = 0.04) and visualization of the common bile duct (4.55 ± 0.60 vs 4.39 ± 0.78, P = 0.034) and pancreatic duct (3.47 ± 1.22 vs 3.26 ± 1.32, P = 0.025), but lower background suppression (3.00 ± 0.54 vs 3.37 ± 0.58, P < 0.001) than conventional MRCP. Overall image quality was not significantly different between the 2 examinations (3.51 ± 0.95 vs 3.47 ± 1.09, P = 0.75). The number of indeterminate MRCP examinations for the anatomic variation and disease of the bile duct significantly decreased on CS-MRCP, from 16.7%-22.6% to 9.5%-11.9% and 8.4%-15.6% to 3.6%-8.4% in all readers (P = 0.003-0.03). In the 28 patients who underwent BH-CS-MRCP, better image quality was demonstrated than with conventional MRCP and CS-MRCP (4.10 ± 0.84 vs 3.44 ± 1.21 vs 3.50 ± 1.11, respectively, P = 0.002, 0.001). Sensitivities for detecting bile duct disease was 88.9% to 100% on both BH-CS-MRCP and conventional MRCP (P > 0.05), and for detecting pancreatic disease was 66.7% to 83.3% on BH-CS-MRCP and 50.0% to 72.2% on conventional MRCP (P = 0.002 in reader 1, 0.06-0.47 in readers 2-3). CONCLUSIONS: Compressed sensing MRCP using incoherent undersampling combined with CS reconstruction provided comparable image quality to conventional MRCP while reducing the acquisition time to within a single breath-hold (16 seconds).

Clinical Feasibility of Free-Breathing Dynamic T1-Weighted Imaging With Gadoxetic Acid-Enhanced Liver Magnetic Resonance Imaging Using a Combination of Variable Density Sampling and Compressed Sensing.

OBJECTIVES: The purpose of the study was to investigate the clinical feasibility of free-breathing dynamic T1-weighted imaging (T1WI) using Cartesian sampling, compressed sensing, and iterative reconstruction in gadoxetic acid-enhanced liver magnetic resonance imaging (MRI). MATERIALS AND METHODS: This retrospective study was approved by our institutional review board, and the requirement for informed consent was waived. A total of 51 patients at high risk of breath-holding failure underwent dynamic T1WI in a free-breathing manner using volumetric interpolated breath-hold (BH) examination with compressed sensing reconstruction (CS-VIBE) and hard gating. Timing, motion artifacts, and image quality were evaluated by 4 radiologists on a 4-point scale. For patients with low image quality scores (<3) on the late arterial phase, respiratory motion-resolved (extradimension [XD]) reconstruction was additionally performed and reviewed in the same manner. In addition, in 68.6% (35/51) patients who had previously undergone liver MRI, image quality and motion artifacts on dynamic phases using CS-VIBE were compared with previous BH-T1WIs. RESULTS: In all patients, adequate arterial-phase timing was obtained at least once. Overall image quality of free-breathing T1WI was 3.30 ± 0.59 on precontrast and 2.68 ± 0.70, 2.93 ± 0.65, and 3.30 ± 0.49 on early arterial, late arterial, and portal venous phases, respectively. In 13 patients with lower than average image quality (<3) on the late arterial phase, motion-resolved reconstructed T1WI (XD-reconstructed CS-VIBE) significantly reduced motion artifacts (P < 0.002-0.021) and improved image quality (P < 0.0001-0.002). In comparison with previous BH-T1WI, CS-VIBE with hard gating or XD reconstruction showed less motion artifacts and better image quality on precontrast, arterial, and portal venous phases (P < 0.0001-0.013). CONCLUSIONS: Volumetric interpolated breath-hold examination with compressed sensing has the potential to provide consistent, motion-corrected free-breathing dynamic T1WI for liver MRI in patients at high risk of breath-holding failure.

Optimal cut-off value of perfusion parameters for diagnosing prostate cancer and for assessing aggressiveness associated with Gleason score.

To determine cut-off value of dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) parameters for differentiation of prostate malignant from benign and cancer with high-grade Gleason score (GS) (GS>7) from low-grade GS (GS≤7), 35 patients (24 malignant and 11 benign) who underwent DCE-MRI were included. Difference between malignant and benign was statistically significant for all magnetic resonance parameters except Ve. The cut-off values were K(trans)=0.184min(-1), Kep=0.695min(-1), iAUC=4.219mmol/l/min, and ADC=1340.5mm(2)/s. A significant difference in mean values of K(trans) and Kep between cancer with high-grade GS and low-grade GS was also observed. K(trans) and Kep showed a significant correlation with GS.