Multiparametric approach with synthetic MR imaging for diagnosing salivary gland lesions.

PURPOSE: To determine whether synthetic MR imaging can distinguish between benign and malignant salivary gland lesions. METHODS: The study population included 44 patients with 33 benign and 11 malignant salivary gland lesions. All MR imaging was obtained using a 3 Tesla system. The QRAPMASTER pulse sequence was used to acquire images with four TI values and two TE values, from which quantitative images of T1 and T2 relaxation times and proton density (PD) were generated. The Mann-Whitney U test was used to compare T1, T2, PD, and ADC values among the subtypes of salivary gland lesions. ROC analysis was used to evaluate diagnostic capability between malignant tumors (MTs) and either pleomorphic adenomas (PAs) or Warthin tumors (WTs). We further calculated diagnostic accuracy for distinguishing malignant from benign lesions when combining these parameters. RESULTS: PAs demonstrated significantly higher T1, T2, PD, and ADC values than WTs (all p < 0.001). Compared to MTs, PAs had significantly higher T1, T2, and ADC values (all p < 0.001), whereas WTs had significantly lower T1, T2, and PD values (p < 0.001, p = 0.008, and p = 0.003, respectively). T2 and ADC were most effective in differentiating between MTs and PAs (AUC = 0.928 and 0.939, respectively), and T1 and PD values for differentiating between MTs and WTs (AUC = 0.915 and 0.833, respectively). Combining T1 with T2 or ADC achieved accuracy of 86.4% in distinguishing between malignant and benign tumors. Similarly, combining PD with T2 or ADC reached accuracy of 86.4% for differentiating between malignant and benign tumors. CONCLUSIONS: Utilizing a combination of synthetic MRI parameters may assist in differentiating malignant from benign salivary gland lesions.

Intraoperative computed tomography of a resected lung inflated with air to verify safety surgical margin.

BACKGROUND: During sublobar resection for small, indistinct lung cancer, surgeons may be uncertain as to whether or not the target lesion has been resected and the surgical margin is sufficient. We herein report our procedure for confirming the success of sublobar resection without incising the resected specimen. METHODS: We reviewed our initial experience of 12 patients with intrapulmonary lesions (consolidation diameter ≤1 cm) who underwent thoracoscopic pulmonary wedge resection using autostapler. Six patients had primary adenocarcinoma showing part solid lesion, and remaining six patients had metastatic carcinoma showing purely solid lesion. Intraoperatively, the resected specimen was inflated with air and subjected to computed tomography (CT). The maximum tumor diameter and surgical margin length were measured intraoperatively on CT and postoperatively on formalin-fixed specimen. Surgical stump cytology was also done to verify surgical margin. RESULTS: According to the intraoperative CT, complete resection was confirmed in all patients. The intraoperative CT-based maximum tumor diameter closely correlated with the macroscopically measured one (r=0.971, P<0.0001). However, the tumor shrunk after formalin-fixation by 16.0% in patients with primary lung cancer (P<0.01), but not in patients with metastatic lung cancer. The intraoperative CT-based margin length closely correlated with the macroscopically measured one (r=0.984, P<0.0001). However, the margin shrunk after formalin-fixation in both patients with primary lung cancer and metastatic lung cancer, by 15.1% and 15.7%, respectively. Stump cytology was negative in all patients. Consequently, no recurrence was found during postoperative follow-up of 23 months (range, 14-31 months). CONCLUSIONS: Intraoperative CT is reliable for diagnosing the presence of a target lesion within the resected specimen as well as for estimating the surgical margin length in patients undergoing sublobar resection for intrapulmonary indistinct lesions.

Usefulness of dual-layer spectral CT in follow-up examinations: diagnosing recurrent squamous cell carcinomas in the head and neck.

PURPOSE: To evaluate the usefulness of dual-energy analyses using dual-layer spectral CT (DLSCT) for diagnosing recurrent lesions of head and neck squamous cell carcinoma (HNSCC). MATERIALS AND METHODS: The study population comprised 62 patients with a history of HNSCC. Attenuation values on conventional 120-kVp images and 40-keV virtual monochromatic images (VMIs) and iodine concentration (IC) were compared between recurrent lesions and post-treatment changes or non-recurrent nodes using the Mann-Whitney U test. Receiver-operating characteristic (ROC) analysis was used to assess the ability of attenuation values and IC to diagnose recurrent lesions. RESULTS: Attenuation values for 120-kVp and 40-keV images and IC of local recurrent lesions were significantly higher than those of post-treatment changes (p < 0.001), whereas recurrent nodes showed significantly lower attenuation values for both 120 kVp and 40 keV and IC than non-recurrent nodes (p < 0.001). Area under the ROC curves for 120-kVp images, 40-keV images, and IC to diagnose local recurrences were 0.912, 0.992, and 0.984, respectively, and those to diagnose recurrent nodes were 0.819, 0.922, and 0.934, respectively. CONCLUSIONS: Dual-energy images using DLSCT, particularly 40-keV VMIs and IC, may help in diagnosing recurrent lesions of HNSCC.

Visual enhancement pattern during the delayed phase of enhanced CT as an independent prognostic factor in stage IV pancreatic ductal adenocarcinoma.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) has substantial heterogeneity in biophysical features and in outcomes of patients. Identifying reliable pretreatment imaging biomarkers for PDAC with distant metastases (stage IV) is a key imperative. Our objective was to determine whether visual tumor enhancement pattern on enhanced computed tomography (CT) can be used as a prognostic factor in stage IV PDAC treated with chemotherapy. METHODS: This is a retrospective cohort study of 133 patients with stage IV PDAC who underwent multiphasic enhanced CT before systemic chemotherapy. The enhancement pattern of PDAC was qualitatively categorized as hypoattenuation, isoattenuation, or hyperattenuation on each of the pancreatic, portal venous, and delayed phases. The effects of clinical prognostic factors and the visual tumor enhancement pattern on progression-free survival (PFS) and overall survival (OS) were assessed in univariate and multivariate analyses using Cox proportional hazards models. RESULTS: On univariate analysis, the number of metastatic organs and the visual tumor enhancement pattern during the delayed phase were significantly associated with PFS (p = 0.003 and < 0.001, respectively) and OS (p = 0.005 and < 0.001, respectively). Multivariate analysis identified the number of metastatic organs (PFS, p = 0.021; OS, p = 0.041) and visual tumor enhancement pattern during the delayed phase (PFS, p < 0.001; OS, p < 0.001) as independent predictors of PFS and OS. CONCLUSION: Visual enhancement pattern of PDAC on delayed phase enhanced CT appears to be associated with outcomes and could be a useful prognostic factor in stage IV PDAC, despite the need to add the delayed phase to CT protocol for pancreatic disease.

Extracellular volume fraction determined by equilibrium contrast-enhanced dual-energy CT as a prognostic factor in patients with stage IV pancreatic ductal adenocarcinoma.

OBJECTIVES: To evaluate the feasibility of equilibrium contrast-enhanced dual-energy CT (DECT), as compared with single-energy CT (SECT) and to calculate extracellular volume (ECV) fraction to predict the survival outcomes of pancreatic ductal adenocarcinoma (PDAC) patients with distant metastases (stage IV) treated with chemotherapy. METHODS: The study cohort included a total of 66 patients with stage IV PDAC who underwent DECT before systemic chemotherapy between July 2014 and March 2017. Unenhanced and 120-kVp equivalent images during the equilibrium phase were used to calculate tumor SECT-derived ECV fractions, and iodine density images were obtained from equilibrium-phase DECT for DECT-derived ECV fractions. Correlations between SECT- and DECT-derived ECV fractions were identified using the Pearson correlation coefficient and Bland-Altman analysis. The effects of clinical prognostic factors and tumor SECT- and DECT-derived ECV fractions on progression-free survival (PFS) and overall survival (OS) were assessed by univariate and multivariate analyses using Cox proportional hazards models. RESULTS: The correlation between SECT- and DECT-derived ECV fractions was strong (r = 0.965; p < 0.001). The Bland-Altman plot between SECT- and DECT-derived ECV fractions showed a small bias (- 3.4%). Increasing tumor SECT- and DECT-derived ECV fractions were associated with a positive effect on PFS (SECT, p = 0.002; DECT, p = 0.007) and OS (DECT, p = 0.014; DECT, p = 0.015). Only tumor DECT-derived ECV fraction was an independent predictor of PFS (p = 0.018) and OS (p = 0.022) in patients with stage IV PDAC treated with chemotherapy on multivariate analysis. CONCLUSIONS: The ECV fraction determined by equilibrium contrast-enhanced DECT can potentially predict the survival of patients with stage IV PDAC treated with chemotherapy. KEY POINTS: • Extracellular volume fraction of stage IV pancreatic ductal adenocarcinoma determined by dual-energy CT was strongly correlated to that with single-energy CT (r = 0.965, p < 0.001). • Tumor extracellular volume fraction was an independent predictor of progression-free survival (p = 0.018) and overall survival (p = 0.022). • Extracellular volume fraction determined by dual-energy CT could be a useful imaging biomarker to predict the survival of patients with stage IV pancreatic ductal adenocarcinoma treated with chemotherapy.

Estimation of Extracellular Volume Fraction With Routine Multiphasic Pancreatic Computed Tomography to Predict the Survival of Patients With Stage IV Pancreatic Ductal Adenocarcinoma.

OBJECTIVE: This study aimed to determine whether extracellular volume (ECV) fraction with routine equilibrium contrast-enhanced computed tomography (CT) can predict outcomes in patients with stage IV pancreatic ductal adenocarcinoma (PDAC) treated with chemotherapy. METHODS: This is a retrospective cohort study of 128 patients with stage IV PDAC who underwent multiphasic pancreatic CT before systemic chemotherapy. Contrast enhancement and ECV fraction of the primary lesion were calculated using region-of-interest measurement within the PDAC and aorta on unenhanced and equilibrium phase-enhanced CT. The effects of clinical prognostic factors and ECV fractions on progression-free survival (PFS) and overall survival (OS) were assessed by univariate and multivariate analyses using Cox proportional hazards models. RESULTS: The number of metastatic organs and tumor ECV fraction were significant for PFS (P = 0.005 and 0.001, respectively) and OS (P = 0.012 and 0.007, respectively). On the multivariate analysis, multiple metastatic organs (PFS, P = 0.046; OS, P = 0.047) and lower tumor ECV fraction (PFS, P = 0.010; OS, P = 0.026) were identified as independent predictors of poor PFS and OS. CONCLUSION: Extracellular volume fraction with routine equilibrium contrast-enhanced CT may potentially predict survival in patients with stage IV PDAC treated with chemotherapy.

CT and MRI features of undifferentiated carcinomas with osteoclast-like giant cells of the pancreas: a case series.

PURPOSE: The purpose of this case series was to describe computed tomography (CT) and magnetic resonance imaging (MRI) features of undifferentiated carcinoma with osteoclast-like giant cells of the pancreas. METHODS: Institutional ethics review board approval was obtained, and informed consent was waived for this case series. We reviewed CT and MRI of patients with pathologically confirmed undifferentiated carcinoma with osteoclast-like giant cells of the pancreas found in the medical records of our hospital between 2006 and 2016. RESULTS: Seven patients (3 males and 4 females; age, 59-82 years (mean, 71)) with confirmation by surgical resection (n = 3) or biopsy (n = 4) were identified. They underwent CT (n = 7) and MRI (n = 6). The tumors 26-83 mm in diameter (mean, 44 mm) were located in the head (n = 4) or body (n = 3) of the pancreas. They were demonstrated as lower attenuation areas relative to the adjacent pancreas on CT images obtained in both pancreatic and portal vein phases (n = 7) with a well-defined smooth margin (n = 5). They were demonstrated as hypointense areas relative to the pancreas on T2-weighted images (n = 4) and T2*-weighted images (n = 4) and diffusion-weighted images (n = 3). They contained hemosiderin deposits on histology (n = 7). CONCLUSIONS: Undifferentiated carcinoma with osteoclast-like giant cells of the pancreas might be present as low attenuation areas with a well-defined smooth margin on CT images obtained in pancreatic and portal vein phases, and hypointense areas on T2-, T2*-, and diffusion-weighted images caused by hemosiderin deposits.

CT features of parathyroid carcinomas: comparison with benign parathyroid lesions.

PURPOSE: To describe CT features of parathyroid carcinomas (PCs) by comparison with benign parathyroid lesions (BPs). METHODS: This retrospective study comprised 82 patients with 76 BPs (62 adenomas and 14 hyperplastic lesions) and 6 PCs. CT features (size, short-to-long axis ratio, shape, peritumoral infiltration, homogeneity, calcification, attenuation values on unenhanced CT, and contrast enhancement during arterial and venous phases) were compared between PCs and BPs. The diagnostic performance of CT features for diagnosing PCs was calculated for these individual parameters. RESULTS: Short-to-long axis ratio was significantly larger in PCs (0.7 ± 0.1) than in BPs (0.5 ± 0.1, p = 0.004). Irregular shape (33%), the presence of peritumoral infiltration (50%), and calcification (33%) were significantly more common in PCs than BPs. The contrast enhancement value was significantly lower in PCs than BPs during arterial (p = 0.004) and venous phases (p = 0.044). The 100% sensitivity criterion for the short-to-long axis ratio (≥ 0.53), enhancement during arterial phase (≤ 56.6HU), and venous phase (≤ 59.5HU) yielded accuracies (62.1%, 71.9%, and 75.4%, respectively). Irregular shape, peritumoral infiltration, and calcification showed high specificity (98.7%) and accuracy (93.9%, 95.1%, and 93.9%, respectively). CONCLUSIONS: CT features of high short-to-long axis ratio, irregular shape, the presence of peritumoral infiltration and calcification, and low contrast enhancement may aid in distinguishing PCs from BPs.

Extracellular volume fraction determined by equilibrium contrast-enhanced multidetector computed tomography as a prognostic factor in unresectable pancreatic adenocarcinoma treated with chemotherapy.

OBJECTIVES: To assess whether extracellular volume (ECV) fraction with equilibrium contrast-enhanced multidetector computed tomography (MDCT) predicts outcomes for unresectable pancreatic adenocarcinoma patients treated with chemotherapy METHODS: Sixty-seven patients (42 men, 25 women; mean age, 67.5 years; range, 45-83 years) with histologically confirmed surgically unresectable pancreatic adenocarcinoma underwent contrast-enhanced MDCT before systemic chemotherapy. Tumour contrast enhancement (CE) and ECV fraction were calculated using region-of-interest measurement within the pancreatic adenocarcinoma and aorta on unenhanced and equilibrium phase-enhanced CT. The effect on survival variables including age, sex, tumour location, tumour size, TNM stage, carbohydrate antigen (CA) 19-9, carcinoembryonic antigen (CEA), tumour CE and tumour ECV fraction was determined on univariate and multivariate analyses using Cox proportional hazards regression model. RESULTS: Median overall survival was 10.5 months. On univariate analysis, elevated serum CA19-9 (hazard ratio (HR), 1.00; p = 0.006) and CEA (HR, 1.02; p = 0.011) levels were found to be associated with a negative effect on overall survival. Increasing tumour CE (HR, 0.98; p < 0.001) and ECV fraction (HR, 0.97; p = 0.001) were associated with a positive effect. Multivariate analysis revealed that only tumour ECV fraction was an independent predictor of overall survival (HR, 0.97; p = 0.012). CONCLUSIONS: ECV fraction with equilibrium contrast-enhanced MDCT could be a useful imaging biomarker for predicting patient survival after chemotherapy for unresectable pancreatic adenocarcinoma. KEY POINTS: • Tumour aggressiveness and response to therapy are influenced by the extravascular extracellular space. • Extracellular volume (ECV) fraction can be quantified with equilibrium contrast-enhanced CT. • Patients with higher tumour ECV fraction had better prognosis after chemotherapy.

Conspicuity of Malignant Liver Tumors on Diffusion-Weighted Imaging With Short tau Inversion Recovery After Gadolinium Ethoxybenzyl Diethylenetriaminepentaacetic Acid Administration.

BACKGROUND: Diffusion-weighted imaging (DWI) has been used for the detection and characterization of liver tumors because it has excellent contrast resolution. DWI using short tau inversion recovery (STIR) can improve tumor-to-liver contrast after gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) administration that shortens the T1 relaxation of liver parenchyma. PURPOSE: To quantitatively and qualitatively compare the conspicuity of malignant liver tumors on DWI after Gd-EOB-DTPA administration between STIR and chemical shift selective (CHESS) sequences. STUDY TYPE: Single-institution retrospective study. SUBJECTS: Fifty-seven patients with histologically confirmed malignant liver tumors were evaluated. FIELD STRENGTH/SEQUENCE: Low b-value DWIs with STIR and CHESS sequences 18-20 minutes after Gd-EOB-DTPA administration were acquired at 1.5T. ASSESSMENT: Tumor contrast-to-noise ratio (CNR) and visual grade of tumor conspicuity on DWI between STIR and CHESS sequences were compared. STATISTICAL TESTS: Paired Student's t-test and the Wilcoxon signed rank-test were applied. P < 0.05 was considered statistically significant. RESULTS: The mean tumor CNR and visual grade of tumor conspicuity on DWI were significantly higher for STIR than for CHESS (both P < 0.001). Regardless of the presence of chronic liver disease, the mean CNR (normal liver 33.5 ± 19.8 vs. 15.7 ± 12.2, P < 0.001; chronic liver disease 19.6 ± 11.0 vs. 9.2 ± 7.8, P < 0.001) and the visual conspicuity grade (normal liver 3.36 ± 0.64 vs. 2.56 ± 0.77, P < 0.001; chronic liver disease 2.94 ± 0.80 vs. 2.25 ± 0.84, P = 0.001) were significantly higher for STIR than for CHESS. Mean CNR and the visual conspicuity grade were also significantly higher for STIR than for CHESS in patients with hepatocellular carcinomas (CNR 18.1 ± 10.5 vs. 8.8 ± 7.2, P < 0.001; visual grade 2.88 ± 0.83 vs. 2.22 ± 0.87, P = 0.001) or metastases (CNR 35.0 ± 19.3 vs. 16.2 ± 13.1, P < 0.001; visual grade 3.45 ± 0.51 vs. 2.59 ± 0.73, P < 0.001). DATA CONCLUSION: DWI using STIR may be more helpful for depicting malignant liver tumors after Gd-EOB-DTPA administration compared with DWI using CHESS. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:565-573.

Whole-tumor apparent diffusion coefficient (ADC) histogram analysis to differentiate benign peripheral neurogenic tumors from soft tissue sarcomas.

BACKGROUND: Apparent diffusion coefficient (ADC) histogram analyses have been used to differentiate tumor grades and predict therapeutic responses in various anatomic sites with moderate success. PURPOSE: To determine the ability of diffusion-weighted imaging (DWI) with a whole-tumor ADC histogram analysis to differentiate benign peripheral neurogenic tumors (BPNTs) from soft tissue sarcomas (STSs). STUDY TYPE: Retrospective study, single institution. SUBJECTS: In all, 25 BPNTs and 31 STSs. FIELD STRENGTH/SEQUENCE: Two-b value DWI (b-values = 0, 1000s/mm2 ) was at 3.0T. ASSESSMENT: The histogram parameters of whole-tumor for ADC were calculated by two radiologists and compared between BPNTs and STSs. STATISTICAL TESTS: Nonparametric tests were performed for comparisons between BPNTs and STSs. P < 0.05 was considered statistically significant. The ability of each parameter to differentiate STSs from BPNTs was evaluated using area under the curve (AUC) values derived from a receiver operating characteristic curve analysis. RESULTS: The mean ADC and all percentile parameters were significantly lower in STSs than in BPNTs (P < 0.001-0.009), with AUCs of 0.703-0.773. However, the coefficient of variation (P = 0.020 and AUC = 0.682) and skewness (P = 0.012 and AUC = 0.697) were significantly higher in STSs than in BPNTs. Kurtosis (P = 0.295) and entropy (P = 0.604) did not differ significantly between BPNTs and STSs. DATA CONCLUSION: Whole-tumor ADC histogram parameters except kurtosis and entropy differed significantly between BPNTs and STSs. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018.

Value of diffusion tensor imaging in differentiating malignant from benign parotid gland tumors.

PURPOSE: To evaluate whether diffusion tensor imaging (DTI) can be used to differentiate malignant parotid gland tumors from the benign ones. MATERIALS AND METHODS: The study population comprised 59 parotid gland tumors (24 Warthin's tumors, 19 pleomorphic adenomas, seven other benign tumors, and nine malignant tumors). Single-shot echo-planar DTI was performed with motion-probing gradients along 30 noncollinear directions (b=1000s/mm2) at 3.0T. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values for benign and malignant tumors were compared using the Mann-Whitney U test. Receiver-operating characteristic (ROC) curve analysis was performed to assess the ability of the ADC and FA values to differentiate malignant tumors from the benign ones. RESULTS: ADC values showed no significant difference between malignant (0.93±0.21×10-3mm2/s) and benign tumors (1.19±0.50×10-3mm2/s) (p=0.225). FA values of malignant tumors were significantly higher than those of benign tumors (0.26±0.06 vs. 0.17±0.05, p<0.001). The area under the ROC curve of FA was significantly greater than that under the curve of ADC (0.884 vs. 0.628, p=0.010). CONCLUSIONS: DTI, particularly FA, can help differentiate malignant parotid gland tumors from the benign ones.

Computed diffusion-weighted MR imaging for visualization of pancreatic adenocarcinoma: Comparison with acquired diffusion-weighted imaging.

OBJECTIVE: To assess the feasibility of computed diffusion-weighted imaging (cDWI) in comparison with directly acquired DWI for visualizing pancreatic adenocarcinomas. MATERIALS AND METHODS: Patients with pancreatic adenocarcinoma underwent DWI at b-values of 0, 1000 (DWI1000), 1500 (DWI1500) and 2000 (DWI2000) s/mm2. From DWIs at b-values of 0 and 1000s/mm2, we generated cDWIs at b-values of 1500 (cDWI1500) and 2000 (cDWI2000) s/mm2. DWI findings of pancreatic adenocarcinomas (clear hyperintensity; hyperintensity with an unclear distal border; and isointensity), the image quality and the tumor to pancreas contrast ratio (CR) were compared between directly acquired DWI and cDWI. RESULTS: Among the 63 included patients, clear hyperintense tumors were seen in 35 on DWI1000, 50 on DWI1500, 50 on cDWI1500, 53 on DWI2000 and 44 on cDWI2000. Incidence of clear hyperintense tumors was significantly higher on cDWI1500 than on DWI1000 (P=0.013). There was no significant difference in the incidence of clear hyperintense tumors between DWI1500 and cDWI1500 (P>0.999), but a lower incidence was seen on cDWI2000 than on DWI2000 (P=0.028). Image quality was lower on cDWI than on DWI at b-values of 1500 (P=0.002) and 2000s/mm2 (P<0.001). The tumor to distal pancreas CR was significantly higher on cDWI2000 than on cDWI1500 (P<0.001), and on cDWI1500 than on DWI1000 (P<0.001). The cDWI showed a significantly higher tumor to distal pancreas CR than DWI at b-values of 1500 (P=0.004) and 2000s/mm2 (P<0.001). CONCLUSIONS: cDWI1500 generated from b-values of 0 and 1000s/mm2 should be considered more effective than DWI1000 and at least as effective as DWI1500.

ADC histogram analysis for adrenal tumor histogram analysis of apparent diffusion coefficient in differentiating adrenal adenoma from pheochromocytoma.

PURPOSE: To determine the diagnostic performance of apparent diffusion coefficient (ADC) histogram analysis in diffusion-weighted (DW) magnetic resonance imaging (MRI) for differentiating adrenal adenoma from pheochromocytoma. MATERIALS AND METHODS: We retrospectively evaluated 52 adrenal tumors (39 adenomas and 13 pheochromocytomas) in 47 patients (21 men, 26 women; mean age, 59.3 years; range, 16-86 years) who underwent DW 3.0T MRI. Histogram parameters of ADC (b-values of 0 and 200 [ADC200 ], 0 and 400 [ADC400 ], and 0 and 800 s/mm2 [ADC800 ])-mean, variance, coefficient of variation (CV), kurtosis, skewness, and entropy-were compared between adrenal adenomas and pheochromocytomas, using the Mann-Whitney U-test. Receiver operating characteristic (ROC) curves for the histogram parameters were generated to differentiate adrenal adenomas from pheochromocytomas. Sensitivity and specificity were calculated by using a threshold criterion that would maximize the average of sensitivity and specificity. RESULTS: Variance and CV of ADC800 were significantly higher in pheochromocytomas than in adrenal adenomas (P < 0.001 and P = 0.001, respectively). With all b-value combinations, the entropy of ADC was significantly higher in pheochromocytomas than in adrenal adenomas (all P ≤ 0.001), and showed the highest area under the ROC curve among the ADC histogram parameters for diagnosing adrenal adenomas (ADC200 , 0.82; ADC400 , 0.87; and ADC800 , 0.92), with sensitivity of 84.6% and specificity of 84.6% (cutoff, ≤2.82) with ADC200 ; sensitivity of 89.7% and specificity of 84.6% (cutoff, ≤2.77) with ADC400 ; and sensitivity of 94.9% and specificity of 92.3% (cutoff, ≤2.67) with ADC800 . CONCLUSION: ADC histogram analysis of DW MRI can help differentiate adrenal adenoma from pheochromocytoma. LEVEL OF EVIDENCE: 3 J. Magn. Reson. Imaging 2017;45:1195-1203.

Histogram Analysis of Apparent Diffusion Coefficient in Differentiating Pancreatic Adenocarcinoma and Neuroendocrine Tumor.

The aim of this study was to investigate whether histogram analysis in diffusion-weighted (DW) magnetic resonance imaging (MRI) can help differentiate pancreatic adenocarcinomas from neuroendocrine tumors.Sixty-four patients with histologically confirmed 53 pancreatic adenocarcinomas or 19 neuroendocrine tumors underwent DW MRI. We evaluated the pixel distribution histogram parameters (mean, skewness, kurtosis, and entropy) of the apparent diffusion coefficient (ADC) values derived from b-values of 0 and 200 (ADC200), 0 and 400 (ADC400), or 0 and 800 (ADC800) s/mm(2). Histogram parameters were compared between pancreatic adenocarcinomas and neuroendocrine tumors, and the diagnostic performance was evaluated by using receiver operating characteristic (ROC) analysis.The mean ADC200 and ADC400 were significantly higher in neuroendocrine tumors than in pancreatic adenocarcinomas (P = 0.001 and P = 0.019, respectively). Pancreatic adenocarcinomas showed significantly higher skewness and kurtosis on ADC400 (P = 0.007 and P = 0.001, respectively) and ADC800 (P = 0.001 and P = 0.001, respectively). With all b-value combinations, the entropy of ADC values was significantly higher in pancreatic adenocarcinomas (P < 0.001 for ADC200; P = 0.001 for ADC400; P < 0.001 for ADC800), and showed the highest area under the ROC curve for diagnosing adenocarcinomas (0.77 for ADC200, 0.76 for ADC400, and 0.78 for ADC800).ADC histogram analysis of DW MRI can help differentiate pancreatic adenocarcinomas from neuroendocrine tumors.

Diffusion-weighted MR imaging of the pancreas: optimizing b-value for visualization of pancreatic adenocarcinoma.

OBJECTIVES: To determine the optimal b-value of 3.0-T diffusion-weighted imaging (DWI) for visualizing pancreatic adenocarcinomas METHODS: Fifty-five patients with histologically confirmed pancreatic adenocarcinoma underwent DWI with different b-values (b = 500, 1000, 1500, and 2000 s/mm(2)) at 3.0 T. For each b-value, we retrospectively evaluated DWI findings of pancreatic adenocarcinomas (clear hyperintensity relative to the surrounding pancreas, hyperintensity with an unclear distal border, and isointensity) and image quality, and measured tumour-to-pancreas signal intensity (SI) ratios. DWI findings, image quality, and tumour-to-pancreas SI ratios were compared between the four b-values. RESULTS: There was a significantly higher incidence of tumours showing clear hyperintensity on DWI with b-value of 1500 s/mm(2) than on that with b-value of 1000 s/mm(2) (P < 0.001), and on DWI with b-value of 1000 s/mm(2) than on that with b-value of 500 s/mm(2) (P < 0.001). The tumour-to-distal pancreas SI ratio was higher with b-value of 1500 s/mm(2) than with b-value of 1000 s/mm(2) (P < 0.001), and with b-value of 1000 s/mm(2) than with b-value of 500 s/mm(2) (P < 0.001). A lower image quality was obtained at increasing b-values (P < 0.001); the lowest scores were observed with b-value of 2000 s/mm(2). CONCLUSIONS: The use of b = 1500 s/mm(2) for 3.0-T DWI can improve the delineation of pancreatic adenocarcinomas. KEY POINTS: • Diffusion-weighted imaging (DWI) has been used for diagnosing pancreatic adenocarcinoma • The techniques for DWI, including the choice of b-values, vary considerably • DWI often fails to delineate pancreatic adenocarcinomas because of hyperintense pancreas • DWI with a higher b-value can improve the tumour delineation • The lowest image quality was obtained on DWI with b-value = 2000 s/mm (2).

Pancreatic neuroendocrine tumors: Correlation between the contrast-enhanced computed tomography features and the pathological tumor grade.

OBJECTIVE: To determine whether CT features can predict the pathological tumor grades of pancreatic neuroendocrine tumors (PanNETs) according to the recent WHO classification. MATERIALS AND METHODS: In all, 28 patients with histologically confirmed PanNETs underwent preoperative contrast CT examinations. Thirteen tumors were classified as G1 and 15 as G2. Two radiologists independently evaluated the CT features (tumor delineation, peripancreatic vascular involvement, upstream pancreatic duct dilatation, N (regional lymph node metastasis) and M (distant metastasis) grades, tumor homogeneity, cystic or necrotic change, and tumor conspicuity). The tumor sizes and Hounsfield unit values of all PanNETs during each phase on CT were measured by one radiologist. We compared the CT features between pathological tumor grades using Fisher's exact test for nominal scales and Mann-Whitney U test for ordinal scales or continuous variables. Additionally, we evaluated the performances of the CT findings and their combinations to diagnose G2 tumors. RESULTS: G2 tumors showed significantly larger in tumor size than G1 tumors (p=0.029). All 4 tumors with hepatic metastases were G2. Non-hyperattenuation compared with pancreatic parenchyma during portal venous phase (PVP) was significantly associated with G2 (p=0.016). The accuracy for G2 diagnosis of tumor size (≥20mm), M grade (M1), and tumor conspicuity (non-hyperattenuation during PVP) were 71%, 61%, and 71%, respectively, while the accuracy of their combination was 82%. CONCLUSION: Contrast-enhanced CT features (tumor size, M grade, and tumor conspicuity during PVP) can predict the pathological tumor grades of PanNETs.