Yasuo Amano

Cardiac MR Imaging of Hypertrophic Cardiomyopathy: Techniques, Findings, and Clinical Relevance

Hypertrophic cardiomyopathy (HCM) is a relatively common myocardial genetic disease having a wide variety of symptoms and prognoses. The most serious complications of HCM are sudden cardiac death induced by ventricular arrhythmia or inappropriate changes in blood pressure, and heart failure. Cardiac MR imaging is a valuable imaging method for detecting HCM because of its accurate measurement of wall thickness and myocardial mass without limited view and the unique ability of late gadolinium enhancement (LGE) to identify myocardial fibrosis related to the prognosis of HCM. Tagging and T1 or T2 mapping MR imaging techniques have emerged as quantitative methods for the evaluation of disease severity. In this review, we introduce the MR imaging techniques applied to HCM and demonstrate the typical phenotypes and some morphological characteristics of HCM. In addition, we discuss the clinical relevance of MR imaging for risk stratification and management of HCM.

Three-dimensional Cardiac MR Imaging: Related Techniques and Clinical Applications

Three-dimensional (3D) cardiac magnetic resonance (MR) imaging has several advantages, including the easy coverage of the entire heart without misregistration, reduction of breath-holding times, and availability for postprocessing reconstruction. These advantages are associated with some techniques such as breath-hold or navigator gating and parallel imaging. However, the image quality of 3D cardiac MR images is compromised by the use of a shorter repetition time and parallel imaging. Thus, a steady-state free precession sequence, contrast agent administration, and presaturation pulses are used to maintain the image quality. In this review, we introduce the MR imaging techniques used in 3D cardiac MR imaging and demonstrate the typical 3D cardiac MR images, followed by discussion about their advantages and disadvantages.

Vaginal tumor–vesical fistula detected by dynamic fluorodeoxyglucose-positron emission tomography/computed tomography: A case report

Preoperative fistulas are rare in patients with bladder mucosa-invading gynecological tumors. This is the first reported case of a vesico-vaginal fistula identified using 2-deoxy-2-[fluorine-18]fluoro-d-glucose positron emission tomography/computed tomography (18F-FDG-PET/CT) in a patient with vaginal cancer. A 61-year-old woman with vaginal cancer underwent 18F-FDG-PET/CT for assessment of the mass and lymph nodes. Assessment was difficult because overlap of FDG uptake occurred on 18F-FDG-PET/CT images obtained 60min after FDG injection. However, dynamic 18F-FDG-PET/CT clearly indicated the presence of a vaginal tumor-vesical fistula. This case illustrates the usefulness of dynamic 18F-FDG-PET/CT imaging when assessing a vesico-vaginal fistula.

Non-contrast-enhanced T1 Mapping of Dilated Cardiomyopathy: Comparison between Native T1 Values and Late Gadolinium Enhancement

Purpose: We sought to use non-contrast-enhanced T1 mapping to determine the native T1 values required to identify myocardial fibrosis in patients with dilated cardiomyopathy (DCM). Methods: A total of 25 patients with DCM and 15 healthy controls were enrolled. All subjects underwent T1 mapping using modified look–locker inversion recovery, and the patients underwent late gadolinium-enhancement (LGE) imaging. Basal and mid-ventricular levels were divided into eight segments and the T1 value was measured in each segment. The T1 values of septal segments with LGE were compared with those of the septal segments without LGE, the minimum T1 value of each patient, and the T1 values of the normal septal myocardium. Results: Late gadolinium-enhancement was present in 12 septal segments (24.0%) from 10 patients (40.0%). T1 values were significantly higher in septal segments with LGE than in those without (1373.7 vs. 1288.0 ms; P = 0.035) or in normal septal myocardium (1209.1 ms; P < 0.01). A receiver operating characteristic analysis revealed the appropriate cutoff value of 1349.4 ms for identifying LGE with a sensitivity of 75% and specificity of 92.1%. When the minimum T1 value + 1.2 standard deviation (SD) was used as the threshold, the sensitivity was 75% and specificity was 89.5%. Conclusion: Non-contrast-enhanced T1 mapping can be used for assessment of myocardial fibrosis associated with DCM by using the appropriate threshold.

Hypointense Spleen Associated with Severe Acute Pancreatitis on MR Imaging

Acute pancreatitis is an acute-onset pancreatic or peripancreatic inflammatory disease caused by gall stones, alcohol addiction, fatty diet, viral infection, and so on. In severe acute pancreatitis, systemic inflammatory response syndrome can occur, which is associated with renal impairment, intraperitoneal abscess, sepsis, and multiorgan failure. Recently, splenic density on CT is reported to decrease in patients with severe acute pancreatitis.1 This CT finding may be induced by splenocyte reduction, which is a compensatory reaction to peripheral lymphocyte reduction, damaged B-lymphocytes, and fibroblast infiltration in the spleen.1,2 The spleen shows hypointensity in the neonate on the T1and T2-weighted MR images, whereas the signal intensity markedly increases by 8 months of age on the T2-weighted images in proportion to the development of white pulp and maturation of lymphocytic systems.3 Thus, the splenic signal intensity may change if the lymphocytic systems within or outside the spleen are affected by severe acute pancreatitis. A 66-year-old obese man presented with severe abdominal pain about 2 hours after eating ramen noodles. He had a history of repeated pancreatitis, gall stones, and hepatic abscess, but no hematologic diseases, blood transfusions, granulomatous diseases, or amyloidosis. Laboratory examinations (e.g., serum amylase, 991 U/L; urine amylase, 5435 U/L) and CT made a diagnosis of acute pancreatitis at the grade 2. The spleen showed normal enhancement on CT. Abdominal MR imaging study was performed on a 3T 2 days after the onset. The spleen showed hypointensity on all of the breath-hold T1-weighted imaging (TR, 256 ms; TE, 2.3, 3.5, 4.6 ms) and nonfatsuppressed and fat-suppressed T2-weighted imaging (TR, 4745 and 6725 ms; TE, 90 ms) and diffusion-weighted imaging (TR, infinite; TE, 70 ms, b value = 600 mm2/s) (Fig. 1), especially on the fatsuppressed T2-weighted and diffusion-weighted imaging (Fig. 1E and 1F). The size of the spleen appeared normal. It took 7 weeks to normalize amylase and CT with intensive care (e.g. gabexate mesylate, meropenem hydrate). Among our 24 cases of acute pancreatitis who underwent MR imaging, the present case was one of the two most serious. We have demonstrated hypointense spleen associated with severe acute pancreatitis on MR imaging. Hemosiderosis and amyloidosis also leads to hypointense spleen, but the clinical backgrounds, laboratory data, and contrastenhanced CT and MR imaging of the liver, bone marrow, and intestines can exclude these particular diseases. To our knowledge, this is the first report to indicate the utility of MR imaging for evaluating the inflammatory response syndrome of the spleen in acute pancreatitis. Further investigation is required to confirm the significance of hypointense spleen associated with severe acute pancreatitis on MR imaging.

Relationship between Extension or Texture Features of Late Gadolinium Enhancement and Ventricular Tachyarrhythmias in Hypertrophic Cardiomyopathy

Purpose To evaluate the relationship between extension or texture features of late gadolinium enhancement (LGE) and ventricular tachyarrhythmias in hypertrophic cardiomyopathy (HCM). Materials and Methods Twenty-three patients with HCM were enrolled in this IRB-approved study. The extension of LGE was determined based on the American Heart Association segments model. Texture analysis was performed for 43 myocardial LGE using an open-access software (MaZda, Technical University of Lodz, Institute of Electronics, Poland). The relationship between the extension or texture features of LGE and ventricular tachyarrhythmias was evaluated using unpaired test and receiver-operating characteristic (ROC) analysis. Results Six of 23 patients had a history of ventricular tachyarrhythmias, and 16 patients had LGE. All of the 6 patients with the arrhythmias had more than 4 LGE segments and more LGE segments than those without (p < 0.01). Among 4 texture features, entropy LL was the only discriminator between the 2 patient groups (p < 0.01; threshold, 19624; area under the curve [AUC], 0.72). An ROC analysis gave the number of segments showing LGE a better result (AUC, 0.96) for identification of HCM patients with ventricular tachyarrhythmias than the entropy LL of LGE. Conclusion Patients with HCM and a history of ventricular tachyarrhythmias had a wider extension of LGE, and their entropy LL of LGE was significantly lower than those without. The extension of LGE and texture analysis may provide information about LGE related to ventricular tachyarrhythmias in HCM.