Frequency, outcome, and risk factors of contrast media extravasation in 142,651 intravenous contrast-enhanced CT scans.

OBJECTIVE: To evaluate the frequency, outcome, and risk factors of intravenous contrast media (CM) extravasation during contrast-enhanced CT scans in a large population. METHODS: After institutional review board approval, 142,651 patients (72,976 males and 69,675 females; mean age, 59.9 ± 13.0 years) who underwent contrast-enhanced CT scans with intravenous CM between January 2015 and April 2017 were retrospectively included. The frequency of CM extravasations and their clinical outcomes were investigated. Risk factors of CM extravasation were evaluated using logistic regression with generalized estimating equation analyses. In addition, the frequency and risk factors of large-volume (≥100 ml) CM extravasation were also investigated. RESULTS: CM extravasation occurred in 0.23% (321/142,651) of patients, all of which were of mild degree and resolved without any sequelae through conservative management. Multivariate analysis revealed that female gender [odds ratio (OR) = 1.61; p < 0.001], 60 < age ≤ 70 years (OR = 1.71; p = 0.004) or age > 70 years (OR = 2.49; p < 0.001), patients in general wards (OR = 2.71; p < 0.001) or ICUs (OR = 4.76; p < 0.001), 9.4 < CM viscosity ≤ 10.0 (OR = 1.65; p = 0.015), 10.0 < CM viscosity ≤ 10.6 (OR = 1.60; p = 0.002), and CM viscosity > 16.0 (OR = 2.55, p < 0.001) were independent risk factors for CM extravasation. CONCLUSION: CM extravasation during contrast-enhanced CT scans was uncommon with no substantial clinical consequences. Several risk factors that may have the potential to reduce the occurrence of CM extravasation were identified. KEY POINTS: • The observed frequency of contrast media extravasation during contrast-enhanced CT scans was 0.23% (321/142,651). • Significant risk factors for contrast media extravasation were female gender, age older than 60 years, patients in general wards or ICUs, and the viscosity of contrast media greater than 9.4 mPa∙s. • The main preventive action for contrast media extravasation would be to lower the viscosity of contrast media.

Sub-millisievert CT colonography: effect of knowledge-based iterative reconstruction on the detection of colonic polyps.

OBJECTIVES: To assess the feasibility of ultra-low dose computed tomography colonography (CTC) using knowledge-based iterative reconstruction (IR) and to determine its effect on polyp detection. METHODS: Forty-nine prospectively-enrolled patients underwent ultra-low dose CTC in the supine (100 kVp/20 mAs) and prone positions (80 kVp/20 mAs), followed by same-day colonoscopy. Thereafter, images were reconstructed using filtered back projection (FBP) and knowledge-based IR (IMR; Philips Healthcare, Best, Netherlands) algorithms. Effective radiation dose of CTC was recorded. Pooled per-polyp sensitivity and positive predictive value of three radiologists was analysed and compared between FBP and IMR. Image quality was assessed on a five-point scale and image noise was recorded using standard deviations. RESULTS: Mean effective radiation dose of ultra-low dose CTC was 0.90 ± 0.06 mSv. Eighty-nine polyps were detected on colonoscopy (mean, 8.5 ± 4.7 mm). The pooled per-polyp sensitivity for polyps 6.0-9.9 mm (n = 22) on CTC reconstructed with IMR (36/66, 54.5%) was not significantly different with that using FBP algorithm (34/66, 51.5%) (p = 0.414). For polyps ≥10 mm (n = 35), however, the pooled per-polyp sensitivity on CTC with IMR (73/105, 69.5%) was significantly higher than that with FBP (55/105, 52.4%) (p < 0.001). In particular, the difference of per-polyp sensitivity was statistically significant in intermediate (p = 0.014) and novice (p = 0.003) reviewers. Furthermore, mean image noise of IMR (8.4 ± 6.2 HU) was significantly lower than that of FBP (37.5 ± 13.9 HU) (p < 0.001) and image quality with IMR was significantly better than with FBP in all evaluated segments in all reviewers (all ps < 0.001). CONCLUSIONS: Sub-mSv CTC reconstructed with IMR was feasible for the detection of clinically significant polyps, demonstrating 70% per-polyp sensitivity of polyps ≥10 mm, while allowing significant noise reduction and improvement in image quality compared with FBP reconstruction. KEY POINTS: • Sub-mSv CTC using IMR demonstrated 70% per-polyp sensitivity for polyps ≥10 mm. • CTC using IMR significantly outperformed CTC reconstructed with FBP. • IMR allows significantly more noise reduction and improvement in image quality than FBP.

High liver fibrosis index FIB-4 is highly predictive of hepatocellular carcinoma in chronic hepatitis B carriers.

UNLABELLED: Screening for hepatocellular carcinoma (HCC) is clinically important given that its early detection has remarkable survival benefits. We investigated the possible role of FIB-4, a recently developed noninvasive marker for liver fibrosis based on routine laboratory tests, as a clinical indicator for predicting future HCC among hepatitis B surface antigen (HBsAg) carriers. Our retrospective cohort study involved 986 Korean HBsAg carriers 40 years of age or older who visited Seoul National University Hospital for a health checkup. National medical service claims data were used to determine HCC incidence. Median follow-up time was 5.4 years (interquartile range: 4.4 years). Adjusted for age, sex, body mass index, smoking, alcohol, and antiviral medication for hepatitis B, compared to subjects with FIB-4 <1.25, subjects with 1.7≤ FIB-4 <2.4 showed an adjusted hazard ratio (aHR) of 4.57 (95% confidence interval [CI]: 1.50-13.92) and subjects with FIB-4 ≥2.4 showed an aHR of 21.34 (95% CI: 7.73-58.92) for HCC incidence. FIB-4 was shown to have incremental predictive value to ultrasonographic liver cirrhosis for HCC incidence (C-index: 0.701 vs. 0.831; P = 0.001). FIB-4 was also better predictive of HCC incidence, compared to that of ultrasonographic liver cirrhosis (C-index: 0.775 vs. 0.701; P = 0.040). CONCLUSION: High FIB-4 is a highly predictive risk factor for HCC incidence among Korean HBsAg carriers. FIB-4 is a promising, easily applicable, and cost-effective clinical tool in identifying a subpopulation of HBsAg carriers who are at heightened risk. Our study needs to be replicated in larger future studies on various ethnic groups; nonetheless, our study suggests that FIB-4 may play a valuable role in HCC screening among HBsAg carriers.

Differentiation of intrahepatic mass-forming cholangiocarcinoma from hepatocellular carcinoma on gadoxetic acid-enhanced liver MR imaging.

OBJECTIVES: To determine the different imaging features of intrahepatic mass-forming cholangiocarcinoma (IMCC) from hepatocellular carcinoma (HCC) on gadoxetic acid-enhanced magnetic resonance imaging (MRI). METHODS: This retrospective study was institutional review board approved and the requirement for informed consent was waived. Patients who underwent gadoxetic acid-enhanced MRI with histologically confirmed IMCCs (n = 46) or HCCs (n = 58) were included. Imaging features of IMCCs and HCCs on gadoxetic acid-enhanced MRI including T2- and T1-weighted, diffusion weighted images, dynamic study and hepatobiliary phase (HBP) images were analyzed. Univariate and multivariate logistic regression analyses were performed to identify relevant differentiating features between IMCCs and HCCs. RESULTS: Multivariate analysis revealed heterogeneous T2 signal intensity and a hypointense rim on the HBP as suggestive findings of IMCCs and the wash-in and "portal wash-out" enhancement pattern as well as focal T1 high signal intensity foci as indicative of HCCs (all, p < 0.05). When we combined any three of the above four imaging features, we were able to diagnose IMCCs with 94 % (43/46) sensitivity and 86 % (50/58) specificity. CONCLUSIONS: Combined interpretation of enhancement characteristics including HBP images, morphologic features, and strict application of the "portal wash-out" pattern helped more accurate discrimination of IMCCs from HCCs. KEY POINTS: • Analysis of enhancement characteristics helped accurate discrimination of IMCCs from HCCs. • Wash-out should be determined on the PVP of gadoxetic acid-enhanced MRI. • A hypointense rim on the HBP was a significant finding of IMCCs.

Portomesenteric vein thrombosis after gastric surgery.

BACKGROUND: Postoperative portomesenteric venous thrombosis (PMVT) is a rare but potentially serious complication of gastric surgery. This study analyzed the incidence, characteristics, risk factors, and outcomes of PMVT following gastric surgery. METHODS: Medical records of patients who underwent gastric surgery between January 2007 and December 2012 were reviewed retrospectively. The risk factors of PMVT were analyzed by a logistic regression analysis with control group matched 1:4 by age, sex, and cancer stage and by a Poisson regression analysis with unmatched control group. The resolution rate of PMVT in 12 months was compared between the treatment group and the nontreatment group. RESULTS: The total incidence of PMVT after gastric surgery was 0.67 % (31/4611). Most (54.84 %) PMVT cases were detected within 1 month postoperatively. No accompanying deep vein thrombosis (DVT) was noted. Multivariate comparison with 1:4 matched control showed that combined splenectomy, synchronous malignancy, and intra-abdominal complication were independent risk factors. Advanced stage, combined splenectomy, and synchronous malignancy were independent risk factors in Poisson regression analysis using unmatched controls. The resolution rate of PMVT was not different from patients treated with anticoagulation (n = 6) or antiplatelet therapy (n = 1) and were not significantly different with those of the untreated group [85.7 % (6/7) vs. 82.3 % (14/17), p = 0.935] during 1-year follow up. CONCLUSIONS: PMVT after gastric surgery was associated with advanced cancer stage, combined splenectomy, and synchronous malignancy, but it was not related to laparoscopy or DVT. Significant differences in the natural course of PMVT were not found between the treatment group and observation group.

Diagnostic performance of gadoxetic acid-enhanced liver MR imaging in the detection of HCCs and allocation of transplant recipients on the basis of the Milan criteria and UNOS guidelines: correlation with histopathologic findings.

PURPOSE: To determine whether hepatobiliary phase ( HBP hepatobiliary phase ) imaging can improve the diagnostic performance of gadoxetic acid-enhanced liver magnetic resonance (MR) imaging in the detection of hepatocellular carcinomas ( HCC hepatocellular carcinoma s) and to investigate the accuracy of gadoxetic acid-enhanced MR imaging in the allocation of transplant recipients on the basis of the Milan criteria and United Network for Organ Sharing ( UNOS United Network for Organ Sharing ) guidelines. MATERIALS AND METHODS: This retrospective study had institutional review board approval; the requirement for informed consent was waived. Between June 2008 and June 2011, 63 patients who underwent liver transplantation (LT) were included. All patients underwent a gadoxetic acid-enhanced 3.0-T MR imaging examination of the liver that included HBP hepatobiliary phase images obtained 20 minutes after contrast material administration. Two abdominal radiologists independently assessed two MR imaging data sets to detect HCC hepatocellular carcinoma s: Set 1 included unenhanced and gadoxetic acid-enhanced dynamic images, and set 2 also included HBP hepatobiliary phase images. Patients were allocated into three groups: Those who did not meet the Milan criteria, those who did meet the Milan criteria with additional priority according to UNOS United Network for Organ Sharing guidelines, and those who did meet the Milan criteria without additional priority. Diagnostic performance of each data set in depicting HCC hepatocellular carcinoma s was compared by using jackknife alternative free-response receiver operating characteristics ( JAFROC jackknife alternative free-response receiver operating characteristic s). Sensitivity and accuracy of patient allocation were compared by using generalized estimating equations. RESULTS: Sixty-three HCC hepatocellular carcinoma s were found in 36 of 63 patients. Eight patients were classified as not meeting Milan criteria, 12 as meeting Milan criteria with additional priority, and 43 as meeting Milan criteria without additional priority. For the detection of HCC hepatocellular carcinoma s, reader-averaged figures of merit estimated with JAFROC jackknife alternative free-response receiver operating characteristic s were 0.761 for set 1 and 0.791 for set 2 (P < .001). Addition of HBP hepatobiliary phase images significantly improved sensitivity for the detection of HCC hepatocellular carcinoma s, particularly 1-2-cm HCC hepatocellular carcinoma s (six [20.7%] vs 13 [44.8%] of 29 [P = .008] for reader 1 and eight [27.6%] vs 12 [41.4%] of 29 [P = .041] for reader 2). Accuracy of patient allocation was 88.9% for set 1 and 92.1% for set 2 (P = .151). CONCLUSION: Addition of HBP hepatobiliary phase images can significantly improve the diagnostic performance of gadoxetic acid-enhanced liver MR imaging in the detection of 1-2-cm HCC hepatocellular carcinoma s in liver transplantation candidates. In addition, gadoxetic acid-enhanced MR imaging showed 92.1% accuracy in patient allocation on the basis of the Milan criteria and UNOS United Network for Organ Sharing guidelines.

Prospective comparison of 3T MRI with diffusion-weighted imaging and MDCT for the preoperative TNM staging of gastric cancer.

PURPOSE: To compare the diagnostic performance of 3T magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI) and multidetector-row computed tomography (MDCT) for the preoperative TNM staging of gastric cancer. MATERIALS AND METHODS: This prospective study was approved by our Institutional Review Board. Forty-nine consecutive patients with histologically confirmed gastric cancers underwent MDCT and 3T MRI followed by surgery. MRI without DWI, MRI with DWI, and MDCT were reviewed to determine preoperative TNM staging. Using the pathologic stages as the reference standard, the diagnostic performance of each imaging modality was compared. RESULTS: Diagnostic accuracies of MRI with DWI, MRI without DWI, and MDCT did not show a significant difference (≤T2 vs. ≥T3: 85.1%, 78.7%, and 80.9%; ≤T3 vs. T4: 76.6%, 74.5%, and 72.3%; N-negative vs. N-positive: 76.6%, 66.0%, and 63.8%; M0 vs. M1: all 95.9%, respectively) (P > 0.05). For N staging, MRI with DWI demonstrated higher sensitivity but lower specificity (86.7% and 58.8%, respectively) than MRI without DWI (50.0% and 94.1%) or MDCT (43.3% and 100%) (P < 0.05). CONCLUSION: The diagnostic accuracy of 3T MRI is comparable to that of MDCT for the preoperative TNM staging of gastric cancer, and for assessing LN metastasis, the addition of DWI to conventional MRI may increase the sensitivity.

CT differentiation of poorly-differentiated gastric neuroendocrine tumours from well-differentiated neuroendocrine tumours and gastric adenocarcinomas.

PURPOSE: To evaluate the differential CT features of gastric poorly-differentiated neuroendocrine tumours (PD-NETs) from well-differentiated NETs (WD-NETs) and gastric adenocarcinomas (ADCs) and to suggest differential features of hepatic metastases from gastric NETs and ADCs. MATERIALS AND METHODS: Our study population was comprised of 36 patients with gastric NETs (18 WD-NETs, 18 PD-NETs) and 38 patients with gastric ADCs who served as our control group. Multiple CT features were assessed to identify significant differential CT findings of PD-NETs from WD-NETs and ADCs. In addition, CT features of hepatic metastases including the metastasis-to-liver ratio were analyzed to differentiate metastatic NETs from ADCs. RESULTS: The presence of metastatic lymph nodes was the sole differentiator of PD-NETs from WD-NETs (P = .001, odds ratio = 56.67), while the presence of intact overlying mucosa with mucosal tenting was the sole significant CT feature differentiating PD-NETs from ADCs (P = .047, odds ratio = 15.3) For hepatic metastases, metastases from NETs were more hyper-attenuated than those from ADCs. CONCLUSION: The presence of metastatic LNs and intact overlying mucosa with mucosal tenting are useful CT discriminators of PD-NETs from WD-NETs and ADCs, respectively. In addition, a higher metastasis-to-liver ratio may help differentiate hepatic metastases of gastric NETs from those of gastric ADCs with high accuracy. KEY POINTS: • Presence of metastatic LNs is a useful differentiator of PD-NETs from WD-NETs. • Intact overlying mucosa with mucosal tenting suggests PD-NETs more than gastric ADCs. • Metastatic LNs are larger in size and greater in necrotic volume in PD-NETs. • Hepatic metastases from gastric NETs are more hyper-attenuated than those from ADCs.

CT findings suggesting anastomotic leak and predicting the recovery period following gastric surgery.

OBJECTIVE: To assess diagnostic performance of routine CT for detecting anastomotic leak after gastric surgery, and analyse the relationship between recovery period and CT findings. METHODS: We included 179 patients who underwent immediate CT and fluoroscopy after gastric surgery. Two reviewers retrospectively rated the possibility of leak on CT using a five-point scale focused on predefined CT findings. They also evaluated CT findings. Patients were categorised as: Group I, leak on fluoroscopy; Group II, possible leak on CT but negative on fluoroscopy; Group III, no leak. We analysed the relationship between recovery period and group. RESULTS: Area under the curve for detecting leak on CT was 0.886 in R1 and 0.668 in R2 with moderate agreement (к = 0.482). Statistically common CT findings for leak included discontinuity, large amount of air-fluid and wall thickening at anastomosis site (p < 0.05). Discontinuity at anastomosis site and a large air-fluid collection were independently associated with leak (p < 0.05). The recovery period including hospitalisation and postoperative fasting period was longer in Group I than Group II or III (p < 0.05). Group II showed a longer recovery period than Group III (p < 0.05). CONCLUSIONS: Postoperative routine CT was useful for predicting anastomotic leak using specific findings, and for predicting length of recovery period. KEY POINTS: • Anastomotic leakage remains a significant clinical problem following gastric surgery. • Routine CT without oral contrast is useful for predicting anastomotic leaking. • Wall discontinuity at anastomosis sites was an independent predictor for leaking. • CT is also useful for predicting recovery period following gastric surgery.

Usefulness of a metal artifact reduction algorithm for orthopedic implants in abdominal CT: phantom and clinical study results.

OBJECTIVE. The purpose of this study was to evaluate the usefulness of a metal artifact reduction (MAR) algorithm for orthopedic prostheses in phantom and clinical CT. MATERIALS AND METHODS. An agar phantom with two sets of spinal screws was scanned at various tube voltage (80-140 kVp) and tube current-time (34-1032 mAs) settings. The orthopedic MAR algorithm was combined with filtered back projection (FBP) or iterative reconstruction. The mean SDs in three ROIs were compared among four datasets (FBP, iterative reconstruction, FBP with orthopedic MAR, and iterative reconstruction with orthopedic MAR). For the clinical study, the mean SDs of three ROIs and 4-point scaled image quality in 52 patients with metallic orthopedic prostheses were compared between CT images acquired with and without orthopedic MAR. The presence and type of image quality improvement with orthopedic MAR and the presence of orthopedic MAR-related new artifacts were also analyzed. RESULTS. In the phantom study, the mean SD with orthopedic MAR was significantly lower than that without orthopedic MAR regardless of dose settings and reconstruction algorithms (FBP versus iterative reconstruction). The mean SD near the metallic prosthesis in 52 patients was significantly lower on CT images with orthopedic MAR (28.04 HU) than those without it (49.21 HU). Image quality regarding metallic artifact was significantly improved with orthopedic MAR (rating of 2.60 versus 1.04). Notable reduction of metallic artifacts and better depiction of abdominal organs were observed in 45 patients. Diagnostic benefit was achieved in six patients, but orthopedic MAR-related new artifacts were seen in 30 patients. CONCLUSION. Use of the orthopedic MAR algorithm significantly reduces metal artifacts in CT of both phantoms and patients and has potential for improving diagnostic performance in patients with severe metallic artifacts.

MDCT findings of pancreatic metastases according to primary tumors.

PURPOSE: To describe the clinical and MDCT findings of metastatic pancreatic tumors (MPTs) from various primary malignancies and to determine whether there are characteristic imaging features of MPTs according to the various histologies of primary tumors. MATERIALS AND METHODS: Thirty-six patients with pathologically proven MPTs who underwent MDCT were retrospectively enrolled. Mean survival and factors associated with prolonged survival were analyzed using multivariate Cox regression analysis. MDCT was analyzed for the location, number, margin, and pattern and degree of enhancements of MPTs and main pancreatic duct (MPD) dilatations. Significant differences in CT features among the various histologies of MPTs were determined using the χ (2) or Fisher's exact test. RESULTS: The most common primary tumors metastasized to the pancreas were renal cell carcinomas (RCC) (n = 17), gastric cancers (n = 7), and colorectal cancers (n = 5). Mean survival was significantly different between RCC (106.7 months) and non-RCC (25.1 months) metastases (P < 0.001). A primary tumor of RCC was the only factor associated with prolonged survival (hazard ratio: 0.106, P = 0.003). On MDCT, pancreatic metastases from RCC were frequently multifocal, located at the center of the pancreas, usually homogeneous and well-defined with early wash-in and persistent enhancement; non-RCC metastases tended to be solitary, located off-center (P < 0.05), and appeared as heterogeneous, ill-defined nodules with persistent low attenuation (P < 0.05). CONCLUSION: Various non-RCC tumors as well as RCCs metastasize to the pancreas but a primary tumor of RCC is the only factor associated with prolonged survival. MDCT features of MPTs are significantly different between the RCC and non-RCC metastases, potentially aiding in their differentiation and selection of the most appropriate management options for these patients.

Laparoscopy-assisted pylorus-preserving gastrectomy is better than laparoscopy-assisted distal gastrectomy for middle-third early gastric cancer.

OBJECTIVE: The purpose of this study is to compare the surgical, oncologic safety and the nutritional, functional benefit of laparoscopy-assisted pylorus-preserving gastrectomy (LAPPG) with laparoscopy-assisted distal gastrectomy (LADG) for middle-third early gastric cancers (EGC). BACKGROUND: Of those patients with middle-third EGC, it is still difficult to determine which procedure is better between LADG and LAPPG despite alleged advantages of LAPPG. METHODS: For middle-third EGC, a retrospective analysis was performed comparing those who underwent LADG and those who underwent LAPPG. To evaluate surgical and oncologic safety, clinicopathologic differences including the postoperative morbidity, the pattern of lymph node metastasis and recurrence were analyzed. Postoperative protein, albumin, quantification of abdominal fat area using abdomen computed tomography, and the incidence of postoperative gallstone were compared for the evaluation of functional advantages. RESULTS: The overall postoperative morbidity rate was similar between LADG (n = 176) and LAPPG (n = 116). Delayed gastric emptying was less frequent in LADG than in LAPPG (1.7% vs 7.8%); however, the rates of all the other complications were significantly higher in LADG than in LAPPG (17.0% vs 7.8%). The number of examined lymph nodes and metastatic lymph nodes at each lymph node station was not significantly different and 3-year recurrence-free survival rates were also similar between LADG and LAPPG (98.8% vs 98.2%). Decreases in serum protein and albumin in postoperative 1 to 6 months and abdominal fat area in postoperative 1 year were significantly greater in LADG than in LAPPG. The 3-year cumulative incidence of gallstone was significantly higher in LADG than in LAPPG (6.5% vs 0.0%). CONCLUSIONS: For middle-third EGC, LAPPG can be considered as a better treatment option than LADG in terms of nutritional advantage and lower incidence of gallstone.

Ultra-low peak voltage CT colonography: effect of iterative reconstruction algorithms on performance of radiologists who use anthropomorphic colonic phantoms.

PURPOSE: To analyze the effect of a decrease in computed tomographic (CT) colonographic voltage, from 100 and 120 kVp to 80 kVp and reconstructed with filtered back projection ( FBP filtered back projection ), on radiation dose, image noise, and diagnostic performance in anthropomorphic phantoms and to assess the effect of iterative reconstruction ( IR iterative reconstruction ) algorithms on radiologists' performance for 80-kVp CT colonography. MATERIALS AND METHODS: Seven colon phantoms with 68 simulated polyps (≥6 mm) were scanned at three peak voltage settings (80, 100, 120 kVp) and 10 mAs. Images were reconstructed by using FBP filtered back projection , hybrid statistic-based IR iterative reconstruction , and knowledge-based IR iterative reconstruction algorithms. Effective radiation dose, image noise, and per-polyp sensitivity were recorded and compared by two reviewers with Friedman test, repeated measures analysis of variance, and McNemar test. RESULTS: Median size-specific dose estimate and effective radiation dose of 80-kVp CT colonography was 0.231 mGy and 0.167 mSv, respectively, which was lower than with 100- and 120-kVp CT colonography, with significant difference between 80 and 120 kVp (P = .0005). Image noise (202.0 HU) at 80-kVp FBP filtered back projection CT colonography was significantly higher than at 100-kVp FBP filtered back projection (139.1 HU) and 120-kVp FBP filtered back projection (120.4 HU) (P < .0001). Per-polyp sensitivity (reviewer 1, 14.7% [10 of 68]; reviewer 2, 7.4% [five of 68]) at 80-kVp FBP filtered back projection was significantly lower than at 100-kVp FBP filtered back projection (reviewer 1, 57.4% [39 of 68]; reviewer 2, 39.7% [27 of 68]) and 120-kVp FBP filtered back projection (reviewer 1, 85.3% [58 of 68]; reviewer 2, 83.8% [57 of 68]) (P < .0001). With statistic-based IR iterative reconstruction , image noise at 80 kVp decreased significantly (52.8% [106.7 HU of 202.0 HU]) compared with that at 80-kVp FBP filtered back projection (P < .0001), but per-polyp sensitivity (reviewer 1, 79.4% [54 of 68]; reviewer 2, 66.2% [45 of 68]) at 80-kVp statistic-based IR iterative reconstruction remained significantly lower than at 100-kVp statistic-based IR iterative reconstruction (reviewer 1, 95.6% [65 of 68]; reviewer 2, 86.8% [59 of 68]) (P = .001) and 120-kVp statistic-based IR iterative reconstruction (reviewer 1, 98.5% [67 of 68]; reviewer 2, 89.7% [61 of 68]) (P < .001). For knowledge-based IR iterative reconstruction , per-polyp sensitivity at 80 kVp was improved to 98.5% (67 of 68) and 94.1% (64 of 68), not significantly different from that at 100 kVp (reviewer 1, 100% [68 of 68]; reviewer 2, 95.6% [65 of 68]) and 120 kVp (reviewer 1, 100% [68 of 68]; reviewer 2, 95.6% [65 of 68]) (P > .999). CONCLUSION: A decrease in tube voltage to 80 kVp caused reduction in radiation dose (0.166 mSv) with deterioration in image noise and per-polyp sensitivity. By using a knowledge-based IR iterative reconstruction algorithm, radiologists' performance of 80-kVp CT colonography was acceptable and on par with that at 100- or 120-kVp CT colonography.

MR elastography for noninvasive assessment of hepatic fibrosis: reproducibility of the examination and reproducibility and repeatability of the liver stiffness value measurement.

PURPOSE: To determine the reproducibility of MR elastography (MRE) and the reproducibility and repeatability of the stiffness measurement of MRE in the staging of liver fibrosis. MATERIALS AND METHODS: Ninety-four patients, who underwent liver MRE, were included in this study. The patients were classified into group 1 (n = 47) and group 2 (n = 47) according to our knowledge of their histologic hepatic fibrosis (HF) stage. To analyze the reproducibility of MRE, the group 1 patients underwent MRE twice. In addition, to evaluate the repeatability and reproducibility of the stiffness measurement of MRE, a single observer measured the stiffness values of the second MREs in group 1 twice, and two observers independently measured the stiffness values of MRE in group 2. A 95% Bland-Altman limits of agreement and intraclass correlation coefficients (ICCs) were used to evaluate the reproducibility and repeatability of MRE. RESULTS: In group I, there was no significant difference in the mean liver stiffness values of the first and second MRE examinations, i.e., 3.45 ± 0.25 kPa vs. 3.35 ± 0.23 kPa (p = 0.22). The reproducibility of the MRE examination and the reproducibility and repeatability of the stiffness measurement were high, i.e., the ICCs of each parameter were 0.945, 0.827, and 0.963, respectively, and the 95% limits of agreement were 25.3%, 35.35%, and 18.0%, respectively. CONCLUSION: MRE is a promising tool for evaluating HF and has high reproducibility of the examination as well as reproducibility and repeatability of the stiffness measurements.

Evaluation of hepatic fibrosis using intravoxel incoherent motion in diffusion-weighted liver MRI.

OBJECTIVES: To determine whether intravoxel incoherent motion (IVIM)-diffusion-weighted image (DWI)-derived parameters showed better diagnostic performance than the apparent diffusion coefficient (ADC(total)) for the evaluation of hepatic fibrosis (HF). METHODS: This retrospective study was approved by institutional review board, and informed consent was waived. Fifty-five patients with chronic liver disease who had undergone IVIM-DWI using 8 b-values at 3 T were included. True diffusion coefficient (Dt), pseudo-diffusion coefficient (Dp), perfusion fraction (f), and ADC(total) were calculated. Receiver operating characteristic analysis was performed for all parameters for the HF staging. RESULTS: All parameters showed a significant correlation with the HF stages (-0.31 to -0.72, P < 0.05). All parameters were significantly higher in F0 to F1 than in F4 (P < 0.05). The Dp showed better performance than the ADC(total) in differentiating significant HF (≥F2) from F0 to F1. CONCLUSIONS: The IVIM-derived parameters and ADC(total) showed significant correlation with HF. The D p showed better diagnostic performance for differentiating significant HF than did ADC(total).

High spatial resolution, respiratory-gated, t1-weighted magnetic resonance imaging of the liver and the biliary tract during the hepatobiliary phase of gadoxetic Acid-enhanced magnetic resonance imaging.

PURPOSE: The aim of this study was to demonstrate the clinical feasibility of a recently developed navigator-gated, 3-dimensional gradient echo (3D-GRE) sequence for high-resolution, T1-weighted imaging (HR-T1WI) during the hepatobiliary phase (HBP) of gadoxetic acid-enhanced liver magnetic resonance imaging (MRI). MATERIALS AND METHODS: Eighty-seven consecutive patients who underwent gadoxetic acid-enhanced liver MRI were included in this study. To obtain HR-T1WI (acquired resolution, 1 × 1 × 2 mm), a gated 3D-GRE sequence (gated volumetric interpolated breath-hold examination [VIBE]; Siemens) with fat suppression was performed during the HBP and was then compared with standard breath-hold (BH)-GRE sequence (BH-VIBE). For the respiration gating, the phase ordering using the automatic window selection technique was used. Three readers independently scored the artifacts and the imaging quality (IQ) of both image sets and also classified BH-VIBE images into acceptable or unacceptable IQ. Noise and signal-noise ratio of the BH-VIBE and gated-VIBE sequences were compared, and image quality improvement using gated VIBE compared with BH-VIBE was determined when BH-VIBE shows unacceptable IQ. RESULTS: The gated-VIBE sequence successfully provided HR-T1WI, having diagnosable image quality in all patients except 4 patients in 1 reader (95.4%, 83/87). The gated-VIBE sequence showed relatively higher levels of noise (mean [SD], 6.04 [3.18] vs. 3.57 [0.66]) but similar signal-noise ratio (93.60 [39.47] vs. 100.05 [28.94]) compared with BH-VIBE (P = 0.15). In the qualitative analysis, the gated 3D-GRE sequence showed higher scores for depicting focal liver lesions and the sharpness of the hepatic edges (P < 0.0001) but lower subjective overall IQ than did the BH-VIBE (P < 0.01). However, in the patients showing unacceptable BH-VIBE image quality, the degree of improvement of the IQ using the gated-VIBE technique was significantly higher than that seen in the patients showing acceptable BH-VIBE image quality (P < 0.01). CONCLUSIONS: T1-weighted gated-VIBE showed technical feasibility for HR-T1WI during HBP imaging of gadoxetic acid-enhanced MRI.

Magnetic resonance imaging spectrum of solid pseudopapillary neoplasm of the pancreas.

OBJECTIVE: To describe the magnetic resonance imaging spectrum of solid pseudopapillary tumors (SPTs), with an emphasis on solid SPTs. METHODS: Thirty-two patients with proven SPTs with preoperative magnetic resonance were included. The SPTs were classified into 3 types: solid, cystic, and mixed; and 2 radiologists analyzed the images regarding the morphologic features and enhancement pattern. RESULTS: Of 11 solid SPTs, 9 SPTs (81.8%) were less than 3 cm. Alternatively, of the 18 mixed SPTs and 3 cystic SPTs, 15 SPTs (71.4%) were larger than 3 cm. The predominant imaging features were homogeneous hypoenhancement with a gradually incremental enhancement pattern showing a sharp margin without hemorrhage, whereas those of the mixed SPTs were heterogeneous enhancement showing a sharp margin with internal hemorrhage. CONCLUSION: Solid SPTs frequently present as small, well-defined tumors with a gradual enhancement and without hemorrhage or necrosis, and with features that differ from those of mixed or cystic SPTs.

Added value of diffusion-weighted imaging to MR cholangiopancreatography with unenhanced mr imaging for predicting malignancy or invasiveness of intraductal papillary mucinous neoplasm of the pancreas.

PURPOSE: To investigate the added value of diffusion-weighted imaging (DWI) to magnetic resonance cholangiopancreatography (MRCP) with unenhanced MR imaging for predicting the malignancy or invasiveness of intraductal papillary mucinous neoplasms (IPMNs). MATERIALS AND METHODS: Following Institutional Review Board (IRB) approval, this retrospective study included 52 patients with surgically resected IPMNs and who underwent MRCP, unenhanced MRI, and DWI. Three blinded radiologists evaluated the two image sets, ie, MRCP with unenhanced MR images vs. the combined set with MRCP, unenhanced MR images, and DWI, and scored their confidence for malignancy or for invasiveness of IPMNs. The mean apparent diffusion coefficient (ADC) values of benign IPMNs and of intraductal mucinous carcinomas (IPMCs) were compared. The diagnostic accuracy was calculated using receiver operating characteristic (ROC) curve analysis. RESULTS: The mean ADC of malignant IPMNs (2.05 ± 0.66 × 10(-3) mm(2) /sec) was significantly lower than that of benign IPMNs (2.95 ± 0.32 × 10(-3) mm(2) /sec, P < 0.0001). Invasive IPMCs (1.51 ± 0.32 × 10(-3) mm(2) /sec) showed significantly lower ADC than that of noninvasive IPMCs (2.67 ± 0.23 × 10(-3) mm(2) /sec, P = 0.0003). The area of diffusion restriction was more frequently seen in malignant IPMNs than in benign IPMNs (P < 0.00001). The addition of DWI to MRCP with unenhanced MRI did not show a significant improvement for predicting malignant IPMN (P> 0.05), but resulted in a tendency to improve the diagnostic accuracy for the prediction of invasive IPMN in two observers (P = 0.072, P = 0.085). CONCLUSION: The addition of DWI to MRCP with unenhanced MRI may improve the diagnosis of malignant IPMN and further increase the prediction of invasive IPMC.

Radiologic Imaging of Traumatic Bowel and Mesenteric Injuries: A Comprehensive Up-to-Date Review.

Diagnosing bowel and mesenteric trauma poses a significant challenge to radiologists. Although these injuries are relatively rare, immediate laparotomy may be indicated when they occur. Delayed diagnosis and treatment are associated with increased morbidity and mortality; therefore, timely and accurate management is essential. Additionally, employing strategies to differentiate between major injuries requiring surgical intervention and minor injuries considered manageable via non-operative management is important. Bowel and mesenteric injuries are among the most frequently overlooked injuries on trauma abdominal computed tomography (CT), with up to 40% of confirmed surgical bowel and mesenteric injuries not reported prior to operative treatment. This high percentage of falsely negative preoperative diagnoses may be due to several factors, including the relative rarity of these injuries, subtle and non-specific appearances on CT, and limited awareness of the injuries among radiologists. To improve the awareness and diagnosis of bowel and mesenteric injuries, this article provides an overview of the injuries most often encountered, imaging evaluation, CT appearances, and diagnostic pearls and pitfalls. Enhanced diagnostic imaging awareness will improve the preoperative diagnostic yield, which will save time, money, and lives.

Quantification of hepatic macrosteatosis in living, related liver donors using T1-independent, T2*-corrected chemical shift MRI.

PURPOSE: To evaluate the diagnostic implications of the iterative decomposition of water and fat using echo-asymmetry and the least-squares estimation (IDEAL) technique to detect hepatic steatosis (HS) in potential liver donors using histopathology as the reference standard. MATERIALS AND METHODS: Forty-nine potential liver donors (32 male, 17 female; mean age, 31.7 years) were included. All patients were imaged using the in- and out-of-phase (IOP) gradient-echo (GRE) and IDEAL techniques on a 1.5 T MR scanner. To estimate the hepatic fat fraction (FF), two reviewers performed regions-of-interest measurement in 15 areas of the liver seen on the IOP images and on the IDEAL-FF images. The magnetic resonance imaging (MRI) and pathology values of macrosteatosis were correlated using the Pearson correlation coefficient. We analyzed the diagnostic performance of IOP imaging and IDEAL for detecting HS. RESULTS: The results of the hepatic-FF estimated on IDEAL were well correlated with the histologic degree of macrosteatosis (γ = 0.902, P < 0.001). IDEAL showed 100% sensitivity and 91% specificity for detecting HS, and IOP imaging showed 87.5% sensitivity and 97% specificity, respectively. CONCLUSION: IDEAL is a useful tool for the preoperative diagnosis of HS in potential living liver donors; it can also help to avoid unnecessary biopsies in these patients.