[Influence of Image Reconstruction Method on Image Quality in Digital Breast Tomosynthesis].

PURPOSE: Digital breast tomosynthesis (DBT) imaging uses two types of image reconstruction. methods, i.e., filtered back projection (FBP) method and an iterative reconstruction (IR) method. Although the effect of the difference in the image reconstruction method on the image quality has been reported, these studies were performed using different apparatus or conditions. In this study, we examined the effect of image reconstruction on the image quality using the same equipment under the same conditions. METHOD: We measured reflection artifact, sharpness, signal detection ability, and granularity using DBT-photographed images by both the FBP and the IR methods. RESULT: Although the difference between the two methods was subtle for granularity, IR was found to be superior to FBP in all items tested. CONCLUSION: This study suggested the clinical usefulness of IR over FBP.

Hepatic Hodgkin lymphoma with delayed enhancement on CT and MRI.

Hepatic Hodgkin lymphoma is a rare disease, characterized by the presence of abundant granulofibrous stroma, and its radiological features have rarely been described. We report a 67-year-old man, who presented with liver masses that showed apparent delayed enhancement, along with systemic lymphadenopathy and musculoskeletal lesions. Repeated percutaneous needle biopsy, however, failed to confirm the diagnosis, and surgical biopsy finally revealed small amount of Hodgkin cells and Reed-Sternberg cells. In this report, the radiological features of hepatic Hodgkin lymphoma will be presented and discussed, in correlation with its histological findings.

A case of porphyria cutanea tarda of the liver exhibiting multifocal macrovesicular steatosis in the background of microvesicular steatosis, probably caused by uneven iron accumulation.

A 61-year-old man with chronic hepatitis B and a history of alcohol overconsumption was admitted to our hospital for the scrutiny of multiple echogenic liver nodules. CT and hepatobiliary phase of gadoxetate-enhanced MR imaging revealed no nodular lesions. Quantitative fat fraction images and R2* map of MR imaging suggested homogeneous steatosis and uneven iron deposition in the liver, namely moderately and severely elevated R2* values at the nodules and surrounding background liver, respectively. Biopsy specimens showed macrovesicular fatty liver and less iron deposition at the echogenic nodules, and microvesicular fatty change and more prominent iron deposition at the surrounding liver tissue. The patient's urinary uroporphyrin level was elevated, and the final diagnosis of porphyria cutanea tarda was made. In patients with history of excessive alcohol intake or viral hepatitis, echogenic nodules on ultrasonography along with radiological evidence of absence of space occupying lesions, and presence of excessive intrahepatic fat and iron, might suggest a possible diagnosis of porphyria cutanea tarda.

Preliminary Comparison of Multi-scale and Multi-model Direct Inversion Algorithms for 3T MR Elastography.

PURPOSE: To elucidate whether any differences are present in the stiffness map obtained with a multiscale direct inversion algorithm (MSDI) vs that with a multimodel direct inversion algorithm (MMDI), both qualitatively and quantitatively. MATERIALS AND METHODS: The MR elastography (MRE) data of 37 consecutive patients who underwent liver MR elastography between September and October 2014 were retrospectively analyzed by using both MSDI and MMDI. Two radiologists qualitatively assessed the stiffness maps for the image quality in consensus, and the measured liver stiffness and measurable areas were quantitatively compared between MSDI and MMDI. RESULTS: MMDI provided a stiffness map of better image quality, with comparable or slightly less artifacts. Measurable areas by MMDI (43.7 ± 17.8 cm2) was larger than that by MSDI (37.5 ± 14.7 cm2) (P < 0.05). Liver stiffness measured by MMDI (4.51 ± 2.32 kPa) was slightly (7%), but significantly less than that by MSDI (4.86 ± 2.44 kPa) (P < 0.05). CONCLUSION: MMDI can provide stiffness map of better image quality, and slightly lower stiffness values as compared to MSDI at 3T MRE, which radiologists should be aware of.

Homogeneously enhancing breast lesions on contrast enhanced US: differential diagnosis by conventional and contrast enhanced US findings.

OBJECTIVE: To clarify the details of homogeneously enhancing lesions on contrast-enhanced ultrasonography (CEUS) and also to elucidate whether their differential diagnosis is possible. METHODS: Seventy-three homogeneously enhancing lesions on CEUS were retrospectively selected. Two radiologists first assessed conventional US findings alone in consensus to differentiate malignant vs. benign lesions. Then, qualitative and quantitative CEUS findings were analyzed to determine the useful findings for the differential diagnosis. Determined CEUS findings were applied to the indeterminate lesions based on conventional US findings to see whether CEUS can improve the diagnostic performance. RESULTS: There were 42 cancers (58 %) out of 73. Sensitivity and specificity using conventional US findings alone were 91 and 55 %, respectively. Among the CEUS findings tested, multivariate analysis revealed only the type 3 enhancement pattern, which indicates a larger enhancing area than the precontrast hypoechoic lesion, was related to malignancy (p < 0.05). By adding this information, however, no improvement was achieved in the diagnostic performance as determined by conventional US findings. CONCLUSIONS: Approximately half of the homogeneously enhancing lesions on CEUS are malignant, and differentiation of malignant from benign lesions may be possible, at least to some extent, by meticulous assessment of the conventional US rather than CEUS findings.

Obliteration of the Biliary System after Administration of an Oral Contrast Medium Is Probably due to Regurgitation: A Pitfall on MRCP.

PURPOSE: We retrospectively evaluated the incidence and related factors of obliteration of the lower bile duct after oral administration of contrast medium (OCM) probably resulting from its regurgitation into the biliary system (OCMRB) as observed on images of MR cholangiopancreatography (MRCP). METHODS: We retrospectively analyzed 305 MRCP images in 278 patients obtained between February 2010 and March 2011 using negative OCM with 1.0- and 1.5-tesla clinical units. OCMRB was defined as positive when visualization of the common bile duct was clear on precontrast 2-dimensional (2D) MRCP but obliterated on postcontrast 3-dimensional (3D) MRCP. Two abdominal radiologists reviewed all images in consensus. The incidence of OCMRB was correlated to various clinicoradiological factors. RESULTS: We observed OCMRB on 11 MRCP images in 10 patients (3.6%). Among various clinicoradiological factors, the presence of juxtapapillary diverticula, pneumobilia, and history of intervention to the papilla were suggested as significant factors related to positive OCMRB with multivariate analysis (P < 0.05). CONCLUSION: OCMRB occurs in about 4% of the patients who undergo MRCP, typically in those with juxtapapillary diverticula, pneumobilia, and history of papillary intervention. Acquisition of MRCP images before OCM may secure visualization of the common bile duct in these patients.

MR elastography of the liver at 3.0 T in diagnosing liver fibrosis grades; preliminary clinical experience.

OBJECTIVES: To clarify the usefulness of 3.0-T MR elastography (MRE) in diagnosing the histological grades of liver fibrosis using preliminary clinical data. MATERIALS AND METHODS: Between November 2012 and March 2014, MRE was applied to all patients who underwent liver MR study at a 3.0-T clinical unit. Among them, those who had pathological evaluation of liver tissue within 3 months from MR examinations were retrospectively recruited, and the liver stiffness measured by MRE was correlated with histological results. Institutional review board approved this study, waiving informed consent. RESULTS: There were 70 patients who met the inclusion criteria. Liver stiffness showed significant correlation with the pathological grades of liver fibrosis (rho = 0.89, p < 0.0001, Spearman's rank correlation). Areas under the receiver operating characteristic curve were 0.93, 0.95, 0.99 and 0.95 for fibrosis score greater than or equal to F1, F2, F3 and F4, with cut-off values of 3.13, 3.85, 4.28 and 5.38 kPa, respectively. Multivariate analysis suggested that grades of necroinflammation also affected liver stiffness, but to a significantly lesser degree as compared to fibrosis. CONCLUSIONS: 3.0-T clinical MRE was suggested to be sufficiently useful in assessing the grades of liver fibrosis. KEY POINTS: MR elastography may help clinicians assess patients with chronic liver diseases. Usefulness of 3.0-T MR elastography has rarely been reported. Measured liver stiffness correlated well with the histological grades of liver fibrosis. Measured liver stiffness was also affected by necroinflammation, but to a lesser degree. 3.0-T MRE could be a non-invasive alternative to liver biopsy.

Optimization of scanning parameters for MR elastography at 3.0 T clinical unit: volunteer study.

PURPOSE: We sought to optimize scanning parameters for MR elastography at 3.0 T clinical unit. MATERIALS AND METHODS: 10 volunteers were scanned with various magnetization encoding gradient (MEG) frequencies from 60 to 120 Hz at every 10 Hz, with otherwise fixed parameters (external driver frequency/amplitude = 60 Hz/50 %, 10 mm slice thickness, etc.). Images were qualitatively assessed for the degree of image defects, and also quantitatively for the areas without cross-hatching. After determining optimal MEG frequency, external driver amplitudes of 70 % (vs 50 %) and slice thickness of 8 mm (vs 10 mm) were also tested. With the optimized parameters, scans were repeated 1 week after the initial scan, and the repeatability of the liver stiffness measurement was validated. RESULTS: 80 or 90 Hz was shown to be the best MEG frequency. There were no significant differences in the qualitative and quantitative assessment between the two amplitudes and two slice thicknesses; however, 70 % amplitude resulted in discomfort at the chest wall beneath the external acoustic driver. Thus, MEG 80 (or 90) Hz, amplitude 50 %, and thickness 10 (or 8) mm were considered optimal. Repeatability of the liver stiffness measurement was ±10 % (95 % confidence interval). CONCLUSIONS: With the optimized parameters, repeatability of ±10 % in liver stiffness measurement was obtained.

Measurement consistency of MR elastography at 3.0 T: comparison among three different region-of-interest placement methods.

PURPOSE: To test inter- and intraobserver consistency of liver stiffness measurement on MR elastography (MRE) at 3.0 T. MATERIALS AND METHODS: Two abdominal radiologists independently measured stiffness of the liver on MRE in three volunteers and seven patients with chronic liver diseases using three different region-of-interest (ROI) placement methods. Methods 1 and 2 involved placing circular and free-hand-drawn ROIs, respectively, visually referring to anatomical (three-dimensional T1-weighted) and wave images. Method 3 involved placing ROIs on the fused images of MRE and anatomical images developed on a work station, visually referring to wave images. The inter- and intraobserver consistency was assessed with regression and Bland-Altman analysis. RESULTS: Thirty-eight images were available for measurement in total. As for interobserver consistency, method 3 showed the best regression coefficient, correlation coefficient, and y intercept. The absolute values of the interobserver differences for method 3 were significantly smaller than those of method 1 or method 2 (p < 0.05, each). Intraobserver consistency of method 3 was excellent for both observers. CONCLUSION: Stiffness measurement of the liver on MRE performed with the fusion method at 3.0 T provides the highest inter- and intraobserver consistency.

Image and pathological changes after radiofrequency ablation of invasive breast cancer: a pilot study of nonsurgical therapy of early breast cancer.

BACKGROUND: The surgical treatment of early breast cancer has proceeded to less invasive approaches with better cosmetic results. The current study was undertaken to evaluate the clinical and pathological findings after radiofrequency ablation (RFA) without resection for a longer period of time. METHOD: A total of 14 patients with breast cancer were enrolled. All patients were diagnosed to have invasive ductal carcinoma, and the median breast tumor size was 12 mm (range, 6-20 mm). Six patients received RFA treatment followed by immediate resection and eight patients without resection. The patients without resection were evaluated by ultrasound, MRI, and the pathological findings of a core needle biopsy after RFA. The removed specimens were examined by hematoxylin-eosin (HE) staining and nicotinamide adenine dinucleotide (NADH) diaphorase staining. The median follow-up of the patients was 39.9 months. RESULTS: NADH staining was necessary to diagnose complete tumor cell death in the tissue for 3 months after RFA. However, HE staining alone could confirm the effect without NADH staining more than 6 months after RFA. Post-RFA, MRI scans clearly demonstrated the area as a complete ablated lesion in all patients without resection. The ablated area detected by MRI or ultrasound became gradually smaller. All patients that underwent RFA with no resection were alive without relapse. CONCLUSION: RFA therefore could be an effective alternative to partial mastectomy for early breast cancer. Further research will be necessary to establish the standardization of the indications, as well as the optimal techniques and post treatment evaluation modalities.

Pseudolesion of the liver on gadoxetate disodium-enhanced MR images obtained after transarterial chemoembolization for hepatocellular carcinoma: clinicoradiologic correlation.

OBJECTIVE: The purpose of this study was to elucidate the clinicoradiologic characteristics of pseudolesions of the liver in patients with hepatocellular carcinoma (HCC) treated with transarterial chemoembolization (TACE) as observed on gadoxetate disodium-enhanced MR images. A particular interest was correlation between the pseudolesion characteristics and TACE-MRI interval, during which sequential changes in pseudolesions may be revealed after TACE. MATERIALS AND METHODS: Forty-eight patients with HCC who underwent gadoxetate disodium-enhanced MRI after TACE were retrospectively recruited. Pseudolesions were defined as areas of decreased signal intensity in treated areas on hepatocellular phase images that were confirmed to be nontumorous areas at follow-up. The prevalence and MRI features of pseudolesions were correlated with various clinical parameters, including TACE-MRI interval. RESULTS: Pseudolesions were found in 14 patients (29%). Within 1 month of TACE, the prevalence of pseudolesions was 83%. All of the pseudolesions had arterial enhancement, mimicking residual HCC. After 1 month, the prevalence of pseudolesions decreased, and these pseudolesions tended to exhibit no abnormality in any sequence other than the hepatocellular phase. Results of multivariate analysis suggested that size of HCC (p < 0.0001), duration of postembolization syndrome (p = 0.012), and TACE-MRI interval (p = 0.038) are independent indicators of the presence of pseudolesions. CONCLUSION: The prevalence and appearance of pseudolesions differ at different intervals from TACE. Radiologists need to recognize the clinicoradiologic characteristics to differentiate pseudolesions from true residual or recurrent HCC.

CT differentiation of solid serous cystadenoma vs endocrine tumor of the pancreas.

AIM: To differentiate between solid serous cystadenoma (SSCA) and endocrine tumor (ET) of the pancreas using dynamic CT findings. MATERIALS AND METHODS: Between 2001 and 2008, there were 3 SSCA and 15 ET surgically resected in our institute, for whom preoperative multidetector-row CT were available. Various CT features were retrospectively evaluated by two radiologists in consensus for the differentiation between the two entities. Delay time for early and delayed phase images were 40 and 180 or 240s, respectively. For qualitative assessment, density of the tumors relative to the surrounding parenchyma was evaluated, along with other characteristic features. In patients for whom digital data were available, CT values of the tumors were measured, and quantitative assessment was also performed. Relative and absolute washout rate (RWR and AWR, respectively) were also calculated. RESULTS: Mean sizes of the two groups were similar. Tumors were seen as low density area more frequently in SSCA than in ET on unenhanced CT (3/3 vs 1/14), and also on the delayed phase image (2/3 vs 0/14) (p<0.05). Fibrous capsule was observed more frequently in SSCA (2/3) than in ET (0/14). CT value of the tumor on unenhanced CT was significantly lower, and RWR was higher in SSCA than in ET (p<0.05, Mann-Whitney's U test). The difference in delayed phase CT density and AWR did not reach statistically significant level. CONCLUSION: Unenhanced and enhanced CT findings may be of value in differentiation between SSCA and ET.

Papillary renal cell carcinoma with extensive paraaortic nodal metastasis mimicking malignant lymphoma.

A 52-year-old woman with abdominal distension underwent computed tomography (CT) that demonstrated extensive paraaortic lymphadenopathy and a right renal mass. Compared to the renal cortex, the lesions exhibited low signal intensity on T(1)- and T(2)-weighted images and high intensity on diffusion-weighted magnetic resonance (MR) images. We suspected malignant lymphoma and performed excisional biopsy, which revealed metastatic papillary renal cell carcinoma. Retrospectively, significantly reduced signal on in-phase chemical shift MR images compared to out-of-phase images suggested the presence of intratumoral hemosiderin, a characteristic finding of this entity.

Multinodular pseudolymphoma of the liver: computed tomography and magnetic resonance imaging findings.

A 60-year-old woman who had had a history of renal cell carcinoma with intraperitoneal recurrence presented with multiple liver masses. Computed tomography demonstrated multiple enhancing lesions in the both lobes of the liver, and there was an apparent small vessel coursing within one of the lesions. On magnetic resonance imaging, masses showed slight T1 and T2 prolongation, and restricted diffusion: On the hepatobiliary phase of liver-specific contrast agent enhancement, lesions were shown as low signal intensity of varying degree. Liver metastases from renal cell carcinoma were suspected, and partial hepatectomy was performed for the superficially located nodules to make a definitive diagnosis. The final pathological diagnosis was reactive lymphoid hyperplasia or pseudolymphoma of the liver.

Pseudolesion of the liver observed on gadoxetate disodium-enhanced magnetic resonance imaging obtained shortly after transarterial chemoembolization for hepatocellular carcinoma.

The purpose of this report was to describe pseudolesions of the liver that mimicked residual hypervascular hepatocellular carcinoma (HCC), as observed on gadoxetate disodium-enhanced magnetic resonance imaging (EOB-MRI) obtained shortly after transarterial chemoembolization (TACE). Between June 2008 and December 2008, three patients underwent MRI within 12 days after TACE to rule out remaining viable cancerous tissue or to assess the treatment effect. In all three patients, nontumorous liver tissue adjacent to the treated HCC exhibited focal arterial enhancement on dynamic phase and subsequent diminished uptake of gadoxetate disodium on hepatocellular phase images, which mimicked residual HCC. All three patients had mild postembolization syndrome at the time of EOB-MRI and showed no evidence of residual or recurrent tumors on follow-up. The findings of these areas may represent transient focal hyperemia and damage to the liver cell function caused by TACE. Radiologists should be aware that EOB-MRI obtained shortly after TACE may show pseudolesions around the treated tumors and should not mistake them for residual or recurrent tumors.

MR diagnosis of steroid cell tumor of the ovary: value of chemical shift imaging.

A 53-year-old asymptomatic woman was found to have a pelvic mass at medical examination. Magnetic resonance (MR) imaging revealed a 4-cm solid mass at the right adnexal region, which showed marked hyperintensity on T(2)-weighted imaging and marked enhancement on post-contrast T(1)-weighted imaging. Chemical-shift imaging showed slight but significant signal loss on out-of-phase images, which suggested the presence of intratumoral lipid. The resected specimen exhibited typical features of steroid cell tumor, and Oil Red O stain was positive for cytoplasmic lipid.