The Optimal Body Size Index with Which to Determine Iodine Dose for Hepatic Dynamic CT: A Prospective Multicenter Study.

PURPOSE: To identify the body size parameter that exhibits the best correlation with aortic and hepatic enhancement at hepatic dynamic computed tomography (CT) in a large patient population enrolled in a multicenter study. MATERIALS AND METHODS: This prospective study was approved by the ethics committee of each of the 31 participating institutions where 1342 patients were enrolled between April 2012 and September 2013. All patients provided either written or oral informed consent. All patients underwent hepatic dynamic CT, which included preenhanced, hepatic arterial phase (HAP), and portal venous phase (PVP) scanning, performed with the routine scanning protocol of each institution. Changes in CT number (in Hounsfield units) per gram of iodine in the aorta (eA/I) and liver (eL/I) during HAP and PVP scanning were recorded for each patient. Hierarchical multivariate linear regression analysis was performed in which the outcome variable was either eA/I or eL/I; the independent variables were age, sex, one body size parameter (height, body weight, body mass index, lean body weight [LBW], or body surface area), and liver function (aspartate aminotransferase, albumin, and total bilirubin levels). A two-level hierarchical model in which patients were level 1 and the institution was level 2 was used. RESULTS: Hierarchical multivariate linear regression analysis revealed that in the population not stratified by sex, body size was significantly correlated with eA/I and eL/I (P < .001) and that LBW exhibited the strongest correlation with eA/I and eL/I (r = -0.561 and r = -0.601, respectively). Sex-stratified analysis showed that LBW was more strongly correlated with eA/I and eL/I in women (r = -0.779 and r = -0.948, respectively) than in men (r = -0.500 and r = -0.494, respectively) or in the nonstratified total population. CONCLUSION: Among body size parameters, LBW exhibited the strongest correlation with aortic and hepatic enhancement, especially in women.

Diffusion kurtosis imaging of the pancreas for the assessment of HbA1c levels.

PURPOSE: To evaluate the feasibility of diffusion kurtosis (DK) imaging of the pancreas for the assessment of hemoglobin (Hb) A1c values. MATERIALS AND METHODS: Our Institutional Review Board approved this prospective study and written informed consent was obtained. In all, 102 consecutive patients with suspected pancreatic disease underwent magnetic resonance imaging (MRI), including DK imaging. Patients were classified into three groups according to American Diabetes Association criteria: HbA1c < 5.7% (group 1), 5.7% ≤ HbA1c < 6.5% (group 2), and HbA1c ≥ 6.5% (group 3). Mean kurtosis (MK) and apparent diffusion coefficient (ADC) of pancreatic parenchyma were computed. MRI measurements and HbA1c values were then compared. RESULTS: HbA1c values positively correlated with MK (r = 0.66, P < 0.0001). Group 3 was significantly (P < 0.05) higher (P < 0.05) in MK than groups 1 and 2. The sensitivity, specificity, and area under the ROC curve of the MK for the detection of group 3 were 90%, 88%, and 0.92, respectively. CONCLUSION: The MK measurement on DK imaging of the pancreas could be a potential biomarker for assessing HbA1c level.

Findings in pancreatic MRI associated with pancreatic fibrosis and HbA1c values.

PURPOSE: To evaluate the diagnostic performance of noncontrast-enhanced magnetic resonance imaging (MRI) to grade pancreatic fibrosis and to assess hemoglobin (Hb) A1c values. MATERIALS AND METHODS: Twenty-nine consecutive patients with pancreatic or biliary malignancy who underwent pancreatectomy were evaluated. Patients were classified into three groups: HbA1c < 5.7 (group 1), 5.7 ≤ HbA1c < 6.5 (group 2), and HbA1c ≥ 6.5 (group 3). MRI of the pancreas was performed using a 1.5T MR system. The pancreas-to-muscle signal intensity ratio (SIR) on in- and opposed-phase T1 -, T2 -, and diffusion-weighted images, as well as the apparent diffusion coefficient were calculated. MRI measurements, degrees of pancreatic fibrosis, and HbA1c values were compared using multiple regression analysis and Kruskal-Wallis test. RESULTS: The pancreatic fibrosis grade was negatively correlated with the SIR on in-phase T1 -weighted images (r = -0.67, P = 0.0002). The pancreatic fibrosis grade and HbA1c value were negatively correlated with the SIR on opposed-phase T1 -weighted images (r = -0.47, P = 0.019 and r = -0.51, P = 0.0089, respectively). SIRs on in- and opposed-phase T1 -weighted images were significantly lower in group 3 than in groups 1 and 2 (P < 0.05). CONCLUSION: The pancreas-to-muscle SIRs on in- and opposed-phase T1 -weighted images could be a potential biomarker for pancreatic fibrosis and elevated HbA1c values.

Minimally Required Iodine Dose for the Detection of Hypervascular Hepatocellular Carcinoma on 80-kVp CT.

OBJECTIVE: The objective of our study was to determine the iodine dose per unit of body weight (BW) or body surface area (BSA) that is minimally required to detect hypervascular hepatocellular carcinoma (HCC) on 80-kVp CT. SUBJECTS AND METHODS: One hundred eleven patients (78 men and 33 women; mean age, 68 years; age range, 43-85 years) with chronic hepatitis were randomized into three groups with different iodine loads (0.5, 0.4, and 0.3 g I/kg BW) and underwent contrast-enhanced CT at 80 kVp. Enhancement of the liver and of hypervascular HCCs was quantitatively and qualitatively assessed on hepatic arterial, portal venous, and equilibrium phase images and compared between the groups. Values for iodine dose per unit of BSA (g I/m(2)) were also computed and analyzed. RESULTS: No significant differences in the contrast-to-noise ratio (CNR) of hypervascular HCCs in any phase were found between the groups (p = 0.34-0.99). In the portal venous phase, the mean increase in hepatic contrast enhancement (ΔHU) of the 0.5 g I/kg group (80.3 HU) was higher than those of the 0.4 g I/kg (63.4 HU) and 0.3 g I/kg (53.3 HU) groups (p < 0.001). Linear correlation equations for the increase in hepatic contrast enhancement were as follows: ΔHU = 5.9 + 150.0 × IL(BW) (r = 0.69, p < 0.001), where IL(BW) is the iodine load per unit of BW (g I/kg), and ΔHU = 13.0 + 3.68 × IL(BSA) (r = 0.66, p < 0.001), where IL(BSA) is the iodine load pre unit of BSA (g I/m(2)). CONCLUSION: The minimal iodine dose required to achieve a tumor-to-liver CNR that is acceptable for the detection of hypervascular HCCs on 80-kVp CT was 0.3 g I/kg BW or 11.0 g I/m(2) BSA.

MR imaging findings of pilomatricomas: a radiological-pathological correlation.

BACKGROUND: Magnetic resonance imaging (MRI) findings of pilomatricomas have yet to be determined. PURPOSE: To assess the correlation between MRI and pathological findings of pilomatricomas. MATERIAL AND METHODS: MR images were obtained on patients with histologically proven pilomatricomas using a 1.5-T MR scanner. The images were retrospectively reviewed for size, signal intensity compared with skeletal muscles, and enhancement patterns. Furthermore, we assessed the presence of a reticular appearance, a ring-like appearance, and peritumoral fat stranding. RESULTS: We included 11 consecutive patients with 12 histologically proven pilomatricomas (3 boys/men, 8 girls/women; age range, 4-76 years; mean age, 20 years; median age, 14 years). The tumors were located in the head and neck (n = 6), upper extremities (n = 5), and lower extremities (n = 1). The maximum tumor diameter was in the range of 7-32 mm (mean, 16.5 mm). On T2-weighted (T2W) images, five tumors showed homogeneous hypointensity, whereas six showed reticular hyperintensity and one showed cystic hyperintensity. On fat-suppressed T2W images, nine tumors showed reticular hyperintensity, eight showed ring-like hyperintensity, and five showed peritumoral fat stranding. On fat-suppressed gadolinium-enhanced T1-weighted (T1W) images, one tumor showed no enhancement, whereas three showed reticular enhancement and five showed ring-like enhancement. Histologically, edematous and fibrous stroma was observed in 10 tumors, tumor capsules in 11, and inflammatory cell infiltration of the peritumoral fat tissue in nine. CONCLUSION: MRI features of pilomatricomas included reticular and ring-like hyperintensities on fat-suppressed T2W images and reticular and ring-like enhancement on fat-suppressed gadolinium-enhanced T1W images.

Assessment of uterine enhancement rate after abdominal radical trachelectomy using dynamic contrast-enhanced magnetic resonance imaging.

PURPOSE: The purpose of this study was to assess uterine enhancement rate after abdominal radical trachelectomy (ART) using dynamic contrast-enhanced (DCE) magnetic resonance (MR) imaging. METHODS: Ten patients with early uterine cervical cancer, who were treated by ART, were included in this study. Each patient underwent DCE MR imaging using a 3 T unit to assess uterine enhancement rate at three times (before surgery and 1 and 3 months after surgery). The radiologist calculated mean signal intensities of the anterior and posterior myometrium and also measured the signal intensities of the urine in the bladder on the same image, which was expressed as the myometrium-to-urine signal intensity ratio. In the time-intensity ratio curve, enhancement parameters (peak signal intensity ratio and peak time) of the uterine body were compared across the three MR examinations. RESULTS: The peak signal intensity ratio was 6.96 ± 0.98 on MR examinations before surgery, 6.14 ± 0.81 1 month after surgery, and 6.26 ± 0.63 3 months after surgery (p = 0.069). The peak time was 57.6 ± 3.4 s on MR examinations before surgery, 56.4 ± 4.4 s 1 month after surgery, and 53.2 ± 8.0 s 3 months after surgery (p = 0.304). No significant differences were found in either the peak signal intensity ratio or peak time across the three MR examinations. CONCLUSIONS: That no significant decrease of uterine enhancement rate was found after surgery suggests the uterine function and fertility may be preserved after ART.

Usefulness of the dual energy field-in-field technique in breast tangential radiotherapy.

PURPOSE: In the field-in-field (FIF) technique in breast tangential radiotherapy, the energy of the subfield is usually the same as the energy of the main field. However, some studies have applied 10-18 MV to subfields in patients with large breasts. We compared two FIF plans in 66 breast cancer patients: in one, the energy of the subfield was the same as that of the main field (the mono energy plan); in the other, it was higher (the dual energy plan). MATERIALS AND METHODS: The photon energy of the subfield was 6 MV in the mono energy plan and 10 MV in the dual energy plan. The percentage of the planning target volume (PTV) receiving at least 105, 100, and 95% of the prescribed dose (V105, V100, and V95, respectively) was calculated, as were the maximum and mean doses delivered to the PTV (Dmax and Dmean, respectively). Clinical target volumes (CTVs) and the thickness of the breast between the chest wall and skin surface at the level of the nipple were measured. RESULTS: V95% was significantly higher in the dual energy plan than in the mono energy plan in patients with CTVs or breast thickness in the highest quartile. There were no significant differences in the other parameters of the two plans in these patients. CONCLUSION: These findings demonstrate the usefulness of the dual energy FIF technique in patients with large breasts receiving breast tangential radiotherapy.

Diffusion-weighted MR imaging of the pancreas: current status and recommendations.

Advances in image quality over the past few years, mainly due to refinements in hardware and coil systems, have made diffusion-weighted ( DW diffusion weighted ) magnetic resonance (MR) imaging a promising technique for the detection and characterization of pancreatic conditions. DW diffusion weighted MR imaging can be routinely implemented in clinical protocols, as it can be performed relatively quickly, does not require administration of gadolinium-based contrast agents, and enables qualitative and quantitative assessment of tissue diffusivity (diffusion coefficients). In this review, acquisition parameters, postprocessing, and quantification methods applied to pancreatic DW diffusion weighted MR imaging will be discussed. The current common clinical uses of DW diffusion weighted MR imaging (ie, pancreatic lesion detection and characterization) and the less-common applications of DW diffusion weighted MR imaging used for the diagnosis of pancreatic parenchymal diseases will be reviewed. Also, the limitations of the technique, mainly image quality and reproducibility of diffusion parameters, as well as future directions for pancreatic DW diffusion weighted MR imaging will be discussed. The utility of apparent diffusion coefficient ( ADC apparent diffusion coefficient ) measurement for the characterization of pancreatic lesions is now well accepted but there are a number of limitations. Future well-designed, multicenter studies are needed to better determine the most appropriate use of ADC apparent diffusion coefficient in the area of pancreatic disease.

Low-Iodine-Load and Low-Tube-Voltage CT Angiographic Imaging of the Kidney by Using Bolus Tracking with Saline Flushing.

PURPOSE: To prospectively determine the feasibility of low-iodine-load and low-tube-voltage computed tomographic (CT) angiographic imaging of the kidney and to evaluate the opacification and image quality compared with moderate-iodine-load and high-iodine-load techniques. MATERIALS AND METHODS: Institutional review board approval and written informed consent was obtained. One hundred thirteen consecutive patients randomly underwent three protocols for dual-phase renal CT angiographic imaging: high-iodine-load (600 mg iodine per kilogram of body weight at 120 kVp); moderate-iodine-load (400 mg iodine per kilogram of body weight at 80 kVp); and low-iodine-load (contrast agent injection initially prepared at 400 mg iodine per kilogram of body weight but stopped immediately after bolus-tracking trigger at 80 kVp) scanning. CT numbers of vessels and kidneys were measured. CT numbers and signal-to-noise ratio (SNR) were compared with one-way analysis of variance and posthoc Tukey-Kramer test and depiction of vessels and image noise, with Kruskal-Wallis test and pair-wise Mann-Whitney test with Bonferroni correction. RESULTS: Mean iodine weight administered was significantly reduced in order of low- (16.4 g), moderate- (23.5 g), and high-iodine-load (33.7 g) protocols (P < .001). Mean CT numbers of abdominal aorta, renal artery, and renal cortex in first phase were significantly lower with high-iodine-load protocol (308, 274, and 132 HU, respectively) than with moderate- (347, 334, and 156 HU, respectively; P = .001-.006) or low-iodine-load (362, 316, and 161 HU, respectively; P = .001-.003) protocol. Mean CT number of renal vein in second phase was significantly lower with low-iodine-load protocol (223 HU) than with moderate- (299 HU; P < .001) or high-iodine-load (258 HU; P = .020). Mean SNR of renal medulla in second phase was significantly lower (P = .019) with moderate-iodine-load protocol (mean SNR, 7.2) than with high-iodine-load protocol (mean SNR, 10.0). No significant difference in image quality grades was found between high-iodine-load (mean grade, 2.6-2.9), moderate-iodine-load (mean grade, 2.6-3.0), and low-iodine-load (mean grade, 2.6-2.9) protocols (P = .018-.31). CONCLUSION: Combined application of low-iodine-load, bolus tracking with saline flushing, and low-tube-voltage scanning is feasible and resulted in substantial reduction of iodine dose for renal CT angiographic imaging without compromising image quality.

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.

18-F fluorodeoxyglucose uptake in positron emission tomography as a pathological grade predictor for renal clear cell carcinomas.

OBJECTIVES: To evaluate the usefulness of Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (18-F FDG-PET/CT) in the prediction of Fuhrman pathological grades of renal clear cell carcinoma (cRCC). METHODS: This retrospective study was approved by our institutional review board, and written informed consent was waived. Thirty-one patients with pathologically proven cRCC underwent 18-F FDG-PET/CT for tumour staging. Maximum standardized uptake value of cRCC (tumour SUVmax) and mean SUV of the liver and spleen (liver and spleen SUVmean) were measured by two independent observers. Tumour SUVmax, tumour-to-liver SUV ratio, and tumour-to-spleen SUV ratio were correlated with the pathological grades. RESULTS: Logistic analysis demonstrated that only the tumour-to-liver SUV ratio was a significant parameter for differentiating high-grade (Fuhrman grades 3 and 4) tumours from low-grade (Fuhrman grades 1 and 2) tumours (P = 0.007 and 0.010 for observers 1 and 2, respectively). Sensitivity, specificity, and positive and negative predictive values for detecting tumours of Fuhrman grades 3 and 4 were 64, 100, 100, and 77%, respectively, for observer 1, and 79, 88, 85, and 83%, respectively, for observer 2. CONCLUSIONS: The tumour-to-liver SUV ratio with 18-F FDG-PET/CT appeared to be a valuable imaging biomarker in the prediction of high-grade cRCC. KEY POINTS: • Tumour SUV max was correlated with the Fuhrman grades. • High-grade tumours have significantly higher SUV max than low-grade tumours. • Tumour-to-liver SUV ratio is useful in the prediction of high-grade cRCC.

Diffusion kurtosis imaging to assess response to treatment in hypervascular hepatocellular carcinoma.

OBJECTIVE: The objective of our study was to compare diffusion kurtosis imaging (DKI) with conventional diffusion-weighted imaging (DWI) for assessing the response to treatment in hypervascular hepatocellular carcinoma (HCC). SUBJECTS AND METHODS: Sixty-two consecutive patients with treated or untreated hypervascular HCC underwent MRI of the liver including DKI (b values of 0, 100, 500, 1000, 1500, and 2000 s/mm(2)). The mean kurtosis (MK) and apparent diffusion coefficient (ADC) values of the hepatic parenchyma and of the HCCs were computed. The detectability of viable HCC based on MK and ADC values was compared. We also assessed the correlation between Child-Pugh grades and MK or ADC values. RESULTS: For a total of 112 HCC nodules (viable, n = 63; nonviable, n = 49), the MK value was significantly higher for the viable group (mean ± SD, 0.81 ± 0.11) than for the non-viable group (0.57 ± 0.11) (p < 0.001). The mean ADC value was significantly lower for the viable group (1.44 ± 0.42 × 10(-3) mm(2)/s) than for the nonviable group (1.94 ± 0.52 × 10(-3) mm(2)/s) (p < 0.001). The sensitivity, specificity, and AUC of the ROC curve for the assessment of HCC viability were greater (p < 0.001) using MK (85.7%, 98.0%, and 0.95, respectively; cutoff value = 0.710) than using ADC (79.6%, 68.3%, and 0.77, respectively; cutoff value = 1.535 × 10(-3) mm(2)/s). Although the ADC of hepatic parenchyma was lower in patients with Child-Pugh grade B or C disease than in those with grade A disease (p = 0.02), no significant difference in MK (p = 0.45) was found among the Child-Pugh grades. CONCLUSION: DKI can be a new option for the assessment of posttherapeutic response in HCC.

MRI of the thyroid for differential diagnosis of benign thyroid nodules and papillary carcinomas.

OBJECTIVE. The purpose of this study was to evaluate the diagnostic performance of MRI in differentiating thyroid papillary carcinomas from benign thyroid nodules. MATERIALS AND METHODS. The study included 36 patients who had solid thyroid nodules detected by thyroid sonography and underwent MRI. A total of 42 solid thyroid nodules, including 28 benign nodules (maximal diameter range, 6-95 mm; mean diameter [± SD], 23.3 ± 18.1 mm) and 14 papillary carcinomas (maximal diameter range, 11-35 mm; mean, 21.7 ± 8.1 mm) were histopathologically diagnosed. The T1 and T2 signal intensity ratio (SIR) of each thyroid nodule was calculated by measuring the mean signal intensity divided by that of paraspinal muscle. Apparent diffusion coefficient (ADC) values of nodules were also computed. The SIRs and ADCs were then compared between benign nodules and papillary carcinomas. RESULTS. The mean T2 SIR (p < 0.0001) and ADC (p < 0.0001) were significantly lower for papillary carcinomas than for benign nodules, but no significant difference was found in T1 SIR (p = 0.54). The sensitivity, specificity, and AUC for the differentiation of papillary carcinomas were 86%, 100%, and 0.929, respectively, on T2 SIR; 93%, 93%, and 0.929, respectively, on ADC; and 93%, 93%, and 0.929, respectively, on combined T2 SIR and ADC. CONCLUSION. Papillary thyroid carcinomas could be accurately differentiated from benign nodules on the basis of MRI T2 SIR or ADC values.

Prenatal MR imaging diagnosis of placental invasion.

PURPOSE: The aim of the study was to evaluate the characteristic imaging features and performance of prenatal magnetic resonance (MR) imaging in the diagnosis of placental invasion. METHODS: This retrospective study was approved by our institutional review board and written informed consent was waived. Twenty-eight patients (age range 26-39 years; mean age, 33.8 ± 3.1 years) with suspected placental invasion underwent prenatal MR imaging, including 7 patients with placental invasion and 21 without. Two radiologists assessed the presence of seven previously described MR imaging findings associated with placental invasion. Sensitivity, specificity, positive and negative predictive values, and accuracy were calculated. The diagnostic performance was also determined by a receiver-operating-characteristic curve analysis. RESULTS: Three MR imaging findings (uterine bulging, heterogeneous signal intensity in the placenta on T2-weighted images, and hypointense intraplacental bands on T2-weighted images) were significantly more common in patients with placental invasion than in those without (P = 0.020-0.023). The presence of at least two of these three imaging findings yielded a sensitivity, specificity, positive and negative predictive values, and accuracy of 100, 86, 67, 95, and 89%, respectively. CONCLUSIONS: The presence of at least two of the three characteristic prenatal MR imaging findings strongly supports a diagnosis of placental invasion.

Evaluation of the field-in-field technique with lung blocks for breast tangential radiotherapy.

Several studies have reported the advantages of the field-in-field (FIF) technique in breast radiotherapy, including dose reduction in the lungs by using lung field blocks. We evaluated the FIF technique with lung blocks for breast tangential radiotherapy. Sixteen patients underwent free breathing (FB) computed tomography (CT), followed by two CT procedures performed during breath hold after light inhalation (IN) and light exhalation (EX). Three radiotherapy plans were created using the FIF technique based on the FB-CT images: one without lung blocks (LB0) and two with lung blocks whose monitor units (MUs) were 5 (LB5) and 10 (LB10), respectively. These plans were copied to the IN-CT and EX-CT images. V20Gy, V30Gy, and V40Gy of the ipsilateral lung and V100%, V95%, and the mean dose (Dmean) to the planning target volume (PTV) were analyzed. The extent of changes in these parameters on the IN-plan and EX-plan compared with the FB-plan was evaluated. V20Gy, V30Gy, and V40Gy were significantly smaller for FB-LB5 and FB-LB10 than for FB-LB0; similar results were obtained for the IN-plan and EX-plan. V100%, V95%, and Dmean were also significant smaller for FB-LB5 and FB-LB10 than for FB-LB0. The extent of changes in V20Gy, V30Gy, and V40Gy on the IN-plan and EX-plan compared with the FB-plan was not statistically significant. Lung blocks were useful for dose reduction in the lung and a simultaneous PTV decrease. This technique should not be applied in the general population.

Fibrosis and postoperative fistula of the pancreas: correlation with MR imaging findings--preliminary results.

PURPOSE: To assess the potential value of magnetic resonance (MR) imaging in evaluating pancreatic fibrosis and predicting the development of postoperative pancreatic fistula. MATERIALS AND METHODS: This retrospective study had institutional review board approval, and the requirement for informed consent was waived. MR images obtained in 29 consecutive patients (15 men, 14 women; mean age, 64.9 years; age range, 21-80 years) who underwent pancreatectomy were evaluated. The pancreas-to-muscle signal intensity (SI) ratio on unenhanced T1- and T2-weighted, dynamic contrast material-enhanced, and diffusion-weighted images and the apparent diffusion coefficient (ADC) of the pancreas were measured. MR imaging parameters were correlated with the degrees of pancreatic fibrosis and expression of activated pancreatic stellate cells (PSCs) by using univariate and multivariate regression analyses and receiver operating characteristic curve analysis. The relationships between the development of postoperative pancreatic fistula and the MR imaging measurements were examined by using logistic regression analysis and the Mann-Whitney U test. RESULTS: Multiple regression analysis showed that pancreas-to-muscle SI ratios on T1-weighted images and ADC values were independently associated with pancreatic fibrosis (r(2) = 0.66, P < .001) and with activated PSC expression (r(2) = 0.67, P < .001). The mean pancreas-to-muscle SI ratio (± standard deviation) on T1-weighted images was higher (P = .0029) for patients with postoperative pancreatic fistula (1.6 ± 0.2) than for those without (1.2 ± 0.2), and the odds ratio for postoperative pancreatic fistula was 21.3 in patients with an SI ratio of 1.41 and higher. CONCLUSION: The pancreas-to-muscle SI ratio on T1-weighted MR images of the pancreas may be a potential biomarker for assessment of pancreatic fibrosis and prediction of postoperative pancreatic fistula.

Consensus report from the 6th International forum for liver MRI using gadoxetic acid.

As the utility of liver-specific magnetic resonance imaging (MRI) increases, it is pertinent to optimize and expand protocols to improve accuracy and foster evolution of techniques; in turn, positive impacts should be seen in patient management. This article reports on the latest expert thinking and current evidence in the field of liver-specific MRI, as discussed at the 6(th) International Forum for Liver MRI, which was held in Vancouver, Canada in September 2012. Topics discussed at this forum described the use of gadoxetic acid-enhanced MRI for the assessment of liver function at the segmental level; to increase accuracy in the diagnosis of liver metastases; to overcome current challenges in patients with cirrhosis, including management of arterial hypo-/isovascular, hepatobiliary phase hypointense nodules; and the data which would be required in order to recommend the use of this modality in hepatocellular carcinoma management guidelines. Growing evidence suggests that gadoxetic acid-enhanced MRI can help to improve the management of patients with a number of different liver disorders; however, more data are needed in some areas, and there may be a case for developing an interpretation guideline for gadoxetic acid-enhanced MRI findings to aid standardization.

Determination of optimal intravenous contrast agent iodine dose for the detection of liver metastasis at 80-kVp CT.

OBJECTIVES: To determine the optimal iodine mass (IM) to achieve a 50-HU increase in hepatic attenuation for the detection of liver metastasis based on total body weight (TBW) or body surface area (BSA) at 80-kVp computed tomography (CT) imaging of the liver. METHODS: One-hundred and fifty patients who underwent contrast-enhanced CT at 80-kVp were randomised into three groups: 0.5 gI/kg, 0.4 gI/kg and 0.3 gI/kg. Portal venous phase images were evaluated for hepatic parenchymal enhancement (∆HU) and visualisation of liver metastasis. Iodine mass per BSA (gI/m(2)) calculated in individual patients were evaluated. RESULTS: Mean ∆HU for the 0.5 gI/kg group (84.2 HU) was higher than in the 0.4 gI/kg (66.1 HU) and 0.3 gI/kg (53.7 HU) groups (P < 0.001). Linear correlation equations between ∆HU and IM per TBW or BSA are ∆HU = 7.0 + 153.0 × IM/TBW (r = 0.73, P < 0.001) and ∆HU = 11.4 + 4.0 × IM/BSA (r = 0.75, P < 0.001), respectively. The three groups were comparable for the visualisation of hepatic metastases. CONCLUSIONS: The iodine mass to achieve a 50-HU increase in hepatic attenuation at 80-kVp CT was estimated to be 0.28 gI/kg of body weight or 9.6 gI/m(2) of body surface area. KEY POINTS: • Hepatic enhancement is expressed as ∆HU = 7.0 + 153.0 × IM [g]/TBW [kg]. • Hepatic enhancement is expressed as ∆HU = 11.4 + 4.0 × IM [g]/BSA [m(2)]. • Essential iodine dose at 80-kVp CT was 0.28 gI/kg or 9.6 gI/m(2).

Whole-body CT angiography with low tube voltage and low-concentration contrast material to reduce radiation dose and iodine load.

OBJECTIVE: The purpose of this study was to prospectively evaluate the contrast enhancement, vascular depiction, image quality, and radiation dose of low-tube-voltage whole-body CT angiography (CTA) performed with low-concentration iodinated contrast material. SUBJECTS AND METHODS: Whole-body CTA was performed on 109 patients with a 64-MDCT scanner. Patients were randomized into three groups: CTA with 240-mg/mL contrast material at 80 kVp (240-80 group), 300-mg/mL at 80 kVp (300-80 group), and 370-mg/mL at 120 kVp (370-120 group). Signal-to-noise ratio (SNR), arterial depiction, image quality, and radiation dose were assessed. Figure of merit was computed to normalize signal-to-noise ratio, estimated effective dose, and iodine weight. RESULTS: In the 240-80 group, the mean load of administered iodine was 21.6 g; for the 300-80 group, 26.8 g; and the 370-120 group, 34.0 g (p < 0.05). The ranges of mean vascular enhancement were 508-521 HU, 546-593 HU, and 435-442 HU (p < 0.05). Arterial depiction and image quality were comparable for the 240-80 and 370-120 groups and were greater for the 300-80 group than the other two groups in selected arteries (p < 0.05). Effective dose was higher (p < 0.05) in the 370-120 group (2.8-5.4 mSv) than in the others (2.3-4.3 mSv). The figure of merit in the 240-80 group was greater than (p < 0.05) or comparable to that in the 370-120 group. CONCLUSION: Use of 240-mg/mL contrast material at 80 kVp seems appropriate for routine whole-body CTA and beneficial for reduction of iodine load and radiation dose, whereas use of 300-mg/mL contrast material may marginally improve delineation of selected small arteries.

Salivary gland tumors of the parotid gland: CT and MR imaging findings with emphasis on intratumoral cystic components.

INTRODUCTION: The purpose of this study was to assess computed tomography (CT) and magnetic resonance (MR) imaging findings of salivary gland tumors of the parotid gland with emphasis on intratumoral cystic components. METHODS: Seventy-two histopathologically confirmed salivary gland tumors of the parotid gland (44 benign and 28 malignant), which underwent both CT and MR imaging including contrast-enhanced study, were included in this study. We retrospectively reviewed images for the presence, number, occupying rate, margin characteristics, distribution, and predominant MR signal intensity of intratumoral cystic components. RESULTS: The prevalence of cystic components was greater in malignant than benign tumors (79 vs. 50%, p < 0.05). The number and occupying rate were similar between benign and malignant tumors. The irregular margins were more frequent in malignant than benign tumors (73 vs. 27%, p < 0.01). The frequency of eccentric location was greater in benign than malignant tumors (91 vs. 55%, p < 0.01), whereas the frequency of centric location was greater in malignant than benign tumors (32 vs. 0%, p < 0.01). On T1-weighted images, the frequency of hyperintensity was greater in benign than malignant tumors (50 vs. 9%, p < 0.01), whereas that of isointensity was greater in malignant than benign tumors (50 vs. 0%, p < 0.01). Multiple logistic regression analysis showed that the absence of irregular margins of cystic components only was significantly correlated with the presence of benign salivary gland tumors (p < 0.01). CONCLUSION: Imaging features of intratumoral cystic components may help to differentiate benign from malignant tumors of the parotid salivary gland.