Yoshifumi Noda

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.

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.

Detection and characterization of focal hepatic lesions with diffusion-weighted MR imaging: a pictorial review.

The purpose of this pictorial review is to discuss the usefulness and limitations of diffusion-weighted (DW) MR imaging of the liver, demonstrating DW images of a variety of focal hepatic diseases. We include hepatocellular carcinoma, borderline-lesions in cirrhosis, metastasis, cavernous hemangioma, cyst, focal nodular hyperplasia, hepatic adenoma, abscess, and hematoma. DW imaging is an important supplementary sequence of routine MR imaging protocols of the liver. Radiologists need to understand its usefulness and limitations in the detection and characterization of benign and malignant focal hepatic diseases.

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.

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.

Characterizing focal hepatic lesions by free-breathing intravoxel incoherent motion MRI at 3.0 T.

Background Diffusion-weighted (DW) imaging is commonly used to distinguish between benign and malignant liver lesions. Purpose To prospectively evaluate the true molecular-diffusion coefficient (D), perfusion-related diffusion coefficient (D*), perfusion fraction (f), and ADC of focal hepatic lesions using a free-breathing intravoxel incoherent motion (IVIM) DW sequence, and to determine if these parameters are useful for characterizing focal hepatic lesions. Material and Methods One hundred and twenty hepatic lesions (34 metastases, 32 hepatocellular carcinoma [HCC], 33 hemangiomas, and 21 liver cysts) in 74 patients were examined. Mean D, D*, f, and ADC values of hepatic lesions were compared among pathologies. ROC curve analyses were performed to assess the performances of D, D*, f, and ADC values for the characterization of liver lesions as benign or malignant. Results The mean D and ADC values of benign lesions were greater than those of malignant lesions (P < 0.001). Although the mean D and ADC values of liver cysts were greater than those of hemangiomas (P < 0.001), and these values were not significantly different between metastases and HCCs (P = 0.99). Area under the ROC curve for ADC values (0.98) was significantly greater (P = 0.048) than that for D values (0.96) for the differentiation of benign and malignant lesions. Sensitivity and specificity for the detection of malignant lesion were 89% and 98%, respectively, when an ADC cut-off value of 1.40 was applied. Conclusion D and ADC values have more potential for characterizing focal hepatic lesions than D* or f values, and for the differentiation of malignancy and benignity.

Reducing iodine load in hepatic CT for patients with chronic liver disease with a combination of low-tube-voltage and adaptive statistical iterative reconstruction

PURPOSE To prospectively assess the effect of reduced iodine load to contrast enhancement, image quality, and detectability of hepatocellular carcinomas (HCCs) in hepatic CT with a combination of 80 kVp tube voltage setting and adaptive statistical iterative reconstruction (ASIR) technique in patients with chronic liver disease. MATERIALS AND METHODS This HIPAA-compliant study was approved by our institutional review board and written informed consent was obtained in all patients. During a recent 9-month period, 170 consecutive patients (114 men and 56 women; age range, 40-85 years; mean, 67.7 years) with suspected chronic liver diseases were randomized into three CT groups according to the following iodine-load and tube-voltage protocols: 600 milligram per kilogram body weight (mg/kg) iodine load and 120 peak kilovolt (kVp) tube voltage setting (600-120 group), 500 mg/kg and 80 kVp (500-80 group), and 400mg/kg and 80 kVp (400-80 group). Analysis of variance was conducted to evaluate differences in CT number, background noise, signal-to-noise ratio (SNR), effective dose, HCC-to-liver contrast-to-noise ratio (CNR), and figure of merit (FOM). Sensitivity, specificity, and area under the receiver-operating-characteristic curve (AUC) were compared to assess the detectability of HCCs. RESULTS Vascular and hepatic enhancement in the 400-80 and 500-80 groups was comparable to or greater than that in the 600-120 group (P<.05). Subjective image quality was comparable among the three groups. Sensitivity, specificity, and AUC for detecting HCCs were comparable among the groups. The effective dose was kept low (3.3-4.1 mSv) in all three groups. CONCLUSION Iodine load can be reduced by 33% in CT of the liver with a combination of 80 kVp tube voltage setting and ASIR technique, without compromising the contrast enhancement, image quality, and detection of HCCs.

Reduction of iodine load in CT imaging of pancreas acquired with low tube voltage and an adaptive statistical iterative reconstruction technique.

Purpose To prospectively assess the contrast enhancement, image quality, radiation dose, and detectability of malignant pancreatic tumors with pancreatic computed tomography (CT) obtained at an 80-kilovolt (peak) (kV[p]) tube voltage setting and reduced iodine dose. Methods Institutional review board approval and written informed consent were obtained. During a recent 10-month period, 136 patients (66 men and 70 women; age range, 21–86 years; mean ± SD age, 65.9 ± 11.0 years) with suspected pancreatic disease were randomized into 3 groups according to the following iodine-load and tube-voltage protocols: 600 mg of iodine per kilogram body weight (mg/kg) and 120 kV(p) (600-120 group), 500 mg/kg and 80 kV(p) (500-80 group), and 400 mg/kg and 80 kV(p) (400-80 group). Analysis of variance was conducted to evaluate differences in CT number, background noise, signal-to-noise ratio, effective dose, lesion-to-pancreas contrast-to-noise ratio, and figure of merit. Sensitivity, specificity, and area under the receiver-operating-characteristic curve were compared to assess the detectability of malignant pancreatic tumors. Results The signal-to-noise ratios in vessels were greater (P < 0.05) in the 400-80 and 500-80 groups than in the 600-120 group, and those in pancreas were comparable between the 400-80 and 600-120 groups. No significant difference was found in effective dose, image quality, lesion-to-pancreas contrast-to-noise ratio, or figure of merit between the groups. Sensitivity, specificity, and area under the receiver-operating-characteristic curve for detecting malignant pancreatic tumors were comparable between the groups. Conclusions Pancreatic CT with an 80-kV(p) setting and 400-mg iodine per kilogram contrast material load facilitates the reduction of iodine dose while maintaining image quality and the detectability of malignant pancreatic tumors.

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.

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

To evaluate the feasibility of diffusion kurtosis (DK) imaging of the pancreas for the assessment of hemoglobin (Hb) A1c values.