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Biomedical subjects

Yasuo Amano

Publications and source records attributed to Yasuo Amano.

18 recordsLinked to original sources
PubMed2006

Differences in null points between the left and right ventricles in contrast-enhanced inversion recovery MR imaging in patients with cardiac diseases.

Delayed contrast-enhanced inversion recovery (IR) gradient-echo MR imaging has been applied to several cardiac diseases, including myocarditis, sarcoidosis, hypertrophic cardiomyopathy, and myocardial damages induced by medical procedures. Although a preliminary study has indicated the usefulness of this imaging for the detection of right ventricular (RV) myocardial damage associated with arrhythmogenic right ventricular cardiomyopathy, the null points of the RV myocardium have not been assessed on contrast-enhanced IR MR imaging. In this study, the null points of the RV and left ventricular (LV) myocardia were evaluated using an IR fast multi-shot echo-planar imaging (Look-Locker sequence) in 26 patients with various cardiac diseases. In nine of the 26 patients, the null points of the RV myocardium were shorter than those of the LV myocardium in the Look-Locker sequence. The RV myocardial signals were significantly higher than the LV myocardial signals in delayed contrast-enhanced MR images. Thus, more attention should be paid to evaluation of the late enhancement of the RV myocardium, and delayed contrast-enhanced MR imaging with a shorter inversion time may be required in some cases.

Adult↗
PubMed2005

Reduction in flow artifacts by using interleaved data acquisition in segmented balanced steady-state free precession cardiac MRI.

Balanced steady-state free precession (SSFP) magnetic resonance (MR) imaging is feasible for cine cardiac images because of the high contrast between myocardium and blood pool and robustness to rapid blood flow. Nonetheless, the flow artifacts are often observed because of off-resonance effects and to in-flow effects of the blood flow. Although reshimming the gradients or readjusting the center frequency reduces the artifacts, the technique can be susceptible for respiratory and cardiac motion and operator-dependent. The purpose of this study is to use another MR imaging technique for the reduction in the flow artifacts in the heart: odd-even interleaved data acquisition in segmented balanced SSFP imaging. The flow artifacts in the ventricle, ghost outside the heart, and visualization of the myocardial border were visually compared between sequential and odd-even interleaved k-space data acquisitions in cine balanced SSFP cardiac MR imaging. The odd-even interleaved k-space data acquisition significantly reduced dark flow artifacts in the left ventricle, improved the visualization of the myocardial border, and was easily installed. This imaging technique should be applied to cine segmented balanced SSFP cardiac MR imaging.

Adult↗
PubMed2005

Brain white matter changes during treatment of a child for acute lymphoblastic leukemia.

A 13-year old boy with acute lymphoblastic leukemia had bilateral paresis of the upper extremities and aphasia 1 week after high dose methotrexate and triple intrathecal therapy (methotrexate, cytarabin, hydrocortisone). The stroke-like neurological symptoms disappeared on the third day. T2-weighted magnetic resonance imaging showed hyperintensities of white matter on the second day. Despite resolution of the neurological symptoms, magnetic resonance images were still abnormal 3 years after the attack. Methotrexate has been considered to be responsible for ischemic damage to oligodendroglial cells, resulting in demyelination. The changes are occasionally prolonged without persistent neurologic symptoms.

Adolescent↗
PubMed2005

Comparison of contrast-enhanced MRI with iodine-123 BMIPP for detection of myocardial damage in hypertrophic cardiomyopathy.

OBJECTIVE: The purpose of this study was to compare contrast-enhanced MRI with dual-radionuclide SPECT for the detection of myocardial damage associated with hypertrophic cardiomyopathy. SUBJECTS AND METHODS: Twenty-three patients with hypertrophic cardiomyopathy were examined. Delayed hyperenhancement of the damaged myocardium was observed using contrast-enhanced MRI, and regional wall thickness and left ventricular ejection fraction were measured using cine balanced steady-state free precession MRI. Dual-radionuclide SPECT using technetium-99m sestamibi and iodine-123 15-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (BMIPP) was performed at rest. In the abnormal myocardial segments, agreement between the contrast-enhanced MRI and 123I BMIPP SPECT was assessed. The relationships between the regional and global cardiac abnormalities and the delayed hyperenhancement on MRI and decreased uptake of 123I BMIPP were also evaluated. RESULTS: In 368 left ventricular segments, 57 segments showed delayed hyperenhancement on MRI, 43 segments showed decreased uptake of 123I BMIPP, and seven showed decreased uptake of (99m)Tc sestamibi. The delayed hyperenhancement and decreased uptake of 123I BMIPP were frequently observed in the interventricular septal wall (p < 0.0001); however, the agreement between the methods in detecting myocardial abnormalities was fair (kappa = 0.38). The abnormal septal walls were significantly thicker than those without apparent abnormalities (p = 0.031). There was an inverse correlation between the number of enhancing segments and the ejection fraction (r = -0.53). CONCLUSION: In hypertrophic cardiomyopathy, contrast-enhanced MRI was valuable for the detection of extensive myocardial damage.

Adult↗
PubMed2004

Magnetic resonance portography using contrast-enhanced fat-saturated three-dimensional steady-state free precession imaging.

PURPOSE: To assess the feasibility of contrast-enhanced fat-saturated three-dimensional steady-state free precession (FIESTA) imaging for contrast-enhanced magnetic resonance (MR) portography. MATERIALS AND METHODS: Contrast-enhanced fat-saturated three-dimensional fast spoiled gradient-echo (SPGR) and FIESTA were performed as MR portography. In 10 cases, fat-saturated three-dimensional FIESTA was first performed and followed by fast SPGR, and the order of post-contrast imaging was reversed in the other 10 cases. Signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) were estimated for portal and visceral veins on the source images. The visualization of portal vein was scored on three-dimensional MR portography. Portal venous system disorders were assessed using three-dimensional MR portography. RESULTS: The SNRs, CNRs, and visual assessment of portal and visceral veins were significantly higher in contrast-enhanced fat-saturated three-dimensional FIESTA than contrast-enhanced fat-saturated three-dimensional fast SPGR (P < 0.05). The contrast-enhanced fat-saturated three-dimensional FIESTA provided high venous signals even at 8 minutes after gadolinium injection. The abnormalities of portal venous system were well visualized with MR portography using contrast-enhanced fat-saturated three-dimensional FIESTA. CONCLUSION: Contrast-enhanced fat-saturated three-dimensional FIESTA was valuable for MR portography, with flexible time window and high vascular signals. This imaging may allow for other post-contrast imaging options before portography and release patients from consecutive breath-holds.

Adult↗
PubMed2004

Delayed hyper-enhancement of myocardium in hypertrophic cardiomyopathy with asymmetrical septal hypertrophy: comparison with global and regional cardiac MR imaging appearances.

PURPOSE: To evaluate the relationship between delayed hyper-enhancement of the myocardium and global and regional cardiac abnormalities in hypertrophic cardiomyopathy (HCM) with asymmetrical septal hypertrophy using magnetic resonance (MR) imaging. MATERIALS AND METHODS: Twenty-three patients with HCM with asymmetrical septal hypertrophy were examined using a 1.5-T MR unit. Contrast-enhanced inversion-recovery gradient-echo imaging was performed to observe the myocardial damages associated with HCM. Balanced steady-state free precession imaging was performed to assess regional wall abnormalities and ejection fraction, and black-blood fast spin-echo imaging was performed to assess left atrial diameter. RESULTS: Delayed hyper-enhancement of the myocardium was primarily observed in the interventricular septal wall. Septal walls with the higher transmural extent of delayed hyper-enhancement were significantly thicker at end-diastole and end-systole (P < 0.05), and tended to show a decreased percentage systolic wall thickening (P = 0.079). There were no differences in theses values between non-enhancing septal walls and septal walls with the transmural extent < 50%. CONCLUSION: The high transmural extent of delayed hyper-enhancement of the myocardium may reflect the severe myocardial damage associated with the regional hypertrophy and hypokinesia in HCM.

Adolescent↗
PubMed2004

MRI of cardiac morphology and function after percutaneous transluminal septal myocardial ablation for hypertrophic obstructive cardiomyopathy.

OBJECTIVE: The objective of our study was to use MRI to show the cardiac morphology and function of patients with hypertrophic obstructive cardiomyopathy after percutaneous transluminal septal myocardial ablation. CONCLUSION: Black blood T2-weighted and contrast-enhanced fast inversion recovery gradient-echo images displayed ablated septal myocardium until 35 weeks after percutaneous transluminal septal myocardial ablation. Central hypointense areas were observed on MRI in patients until 4 weeks after ablation. Black blood and cine steady-state free precession MRI were used to assess the decreased septal wall thickness and diameter of the left atrium after ablation as well as the reduced motion of the ablated region. MRI may be useful for evaluation of cardiac structural, signal, and functional changes associated with percutaneous transluminal septal myocardial ablation.

Adolescent↗
PubMed2003

MR imaging for preoperative diagnosis and assessment of local tumor extent on localized giant cell tumor of tendon sheath.

OBJECTIVE: The purpose of this study was to clarify the usefulness of MR imaging for preoperative diagnosis and evaluation of the extent of localized giant cell tumor of tendon sheath (GCTTS). DESIGN AND PATIENTS: We retrospectively reviewed the MR images of 25 patients with surgically proved GCTTS (seven males and 18 females; mean age, 41 years) including five recurrences. T1- and T2-weighted imaging was carried out on 24 and 22 lesions, respectively. Gadolinium-enhanced images were obtained for 20 lesions. We evaluated the tumor extent around the phalanx (the degree of circumferential occupation by a tumor around the phalanx on an axial plane) and involvement of the bone, joint, and tenosynovial space by both MR imaging and surgery (gold standard). RESULTS: MR signal intensities of the GCTTSs were consistently equal to those of skeletal muscle or between those of muscle and fat on T1-weighted images; on T2-weighted images, the signal intensities tended to be between those of muscle and fat. Most lesions were inhomogeneous due to low-signal-intensity areas, and enhanced following gadolinium administration. The tumor extent around the phalanx was 168.5 +/- 99.2 degrees (63-360 degrees). MR imaging did not identify the bone involvement (five lesions), but depicted the involvement of the joint in four of five lesions and the tenosynovial space in nine of ten lesions. CONCLUSIONS: This study confirms that MR imaging is able to depict the characteristic internal signal of GCTTS. Moreover, it can accurately assess the tumor size and degree of extent around the phalanx, which can affect the type of surgical approach.

Adolescent↗
PubMed2003

Staging of malignant lymphoma with three-station black-blood fast short-inversion time inversion recovery (STIR).

PURPOSE: The purpose of this study was to assess the usefulness of three-station black-blood fast short-inversion time inversion recovery (STIR) imaging in detecting and staging malignant lymphoma. METHODS: Seventeen patients with malignant lymphoma were examined with a 1.5T imager. The findings and stagings determined with three-station black-blood fast STIR imaging were compared with reference standards (e.g., computed tomography [CT] findings and clinical stagings). RESULTS: Three-station black-blood fast STIR imaging provided a fat-suppressed T2-weighted imaging contrast with fewer flow artifacts and revealed nodal involvement as well as bone marrow and spleen involvement to an extent comparable with CT. Especially notable was the excellent specificity (94%) of this imaging technique. Regarding disease staging, significant agreement was observed between clinical staging (k=0.60) and staging as evaluated by three-station black-blood fast STIR, although the detection of lymphadenopathy in the thorax was relatively poor. The average time required for this imaging was approximately 30 min. CONCLUSION: Three-station black-blood fast STIR MR imaging may be useful as a staging tool for malignant lymphoma because this imaging technique reveals lymphoma lesions, which determine the staging, without radiation exposure or the use of contrast agents.

Adult↗
PubMed2003

Centrally fat-saturated three-dimensional magnetic resonance angiography of the abdomen using selective central fat-saturation of k-space.

PURPOSE: To assess the usefulness of centrally fat-saturated three-dimensional magnetic resonance (MR) angiography of the abdomen using an elliptical centric view order and selective placement of fat-saturation pulses in the central 30% portion of the k-space in terms of fat signal reduction, image contrast of post-contrast images, and breath-holding time. METHODS: Fat signal in abdomen and breath-holding time were compared between centrally fat-saturated three-dimensional sequence and partially fat-saturated three-dimensional sequence or conventional fat-saturated three-dimensional sequence. Abdominal contrast-enhanced centrally fat-saturated three-dimensional MR angiography was obtained at arterial and equilibrium phases, and image quality was quantitatively and visually evaluated. RESULTS: Centrally fat-saturated three-dimensional sequence suppressed fat signal, as did the conventional fat-saturated three-dimensional sequence, and the breath-hold was prolonged only by 1.5 seconds compared to the partially fat-saturated three-dimensional sequence. Contrast-enhanced centrally fat-saturated three-dimensional MR angiography provided abdominal MR arteriography with large signal difference between vessels and fat, while venous signal was insufficient at equilibrium phase. CONCLUSION: Abdominal contrast-enhanced centrally fat-saturated three-dimensional MR angiography using an elliptical centric view order and selective central fat-saturation of k-space reduced fat signal comparable to conventional fat-saturated three-dimensional sequence, and provided contrast-enhanced MR arteriography with high vascular contrast and minimum prolongation of breath-hold.

Abdomen↗
PubMed2003

Effects of view ordering and dummy pulse rate on two-dimensional and three-dimensional steady-state free precession imaging.

RATIONALE AND OBJECTIVE: To assess the effects of view ordering and dummy pulse rate on the image quality of steady-state free precession (SSFP) imaging. MATERIAL AND METHODS: Two- and three-dimensional (2D and 3D) SSFP imaging with various view orderings (eg, centric, sequential, reverse centric) and dummy pulse rates were performed in the phantom including several concentrations of gadolinium and patients. RESULTS: Centric view orderings increased the noise in 3D SSFP images in the phantom. In the patients studied, the centric view ordering increased the signals obtained from abdominal organs in 2D and 3D SSFP and the background signal in 3D images, without changing the vascular signals. An increased dummy pulse rate reduced the background signal in 2D SSFP, but not in 3D SSFP. CONCLUSION: Sequential ordering is recommended for both 2D and 3D SSFP, and centric view ordering combined with an increase in dummy pulse rate can be used for 2D imaging.

Aged↗
PubMed2003

Pre-treatment mitotic index versus computer-quantitated Ki-67 nuclear antigen labeling index as predictors of response to neoadjuvant chemotherapy in uterine cervical carcinoma.

In order to evaluate the usefulness of the mitotic index (MI) and the Ki-67 nuclear antigen labeling index (Ki67LI) in pre-treatment biopsy specimens as predictors of response to chemotherapy for uterine cervical carcinomas, twelve patients with squamous cell carcinoma who received neoadjuvant chemotherapy before radical surgery were investigated. The MI and computer-quantitated Ki67LI were determined using H&E and immunostained slides of biopsy specimens collected before chemotherapy. Tumor size was measured three-dimensionally by MR imaging, and assessed before and after chemotherapy. We compared the values of MI and Ki67LI with changes in tumor size and the following results were obtained. 1) The percentage reduction in tumor size ranged from 0 to 98%. The MI ranged from 0.5 to 15, and Ki67LI ranged from 0.01 to 50.1%. 2) A significant positive correlation was observed between response to chemotherapy assessed on MR image and MI [Spearman's correlation coefficient (r) =0.66, n=12, p=0.027], and between response to chemotherapy and Ki67LI (r=0.72, n=12, p=0.017). 3) A significant correlation was observed between MI and computer-assessed Ki67 LI [Pearson's correlation coefficient (r) =0.80, n=12, p=0.002]. Therefore, pre-chemotherapy MI and Ki67LI were both good predictors of response to platinum-based chemotherapy. Because MI is technically more convenient and economically less expensive than computer-quantitated Ki67LI, MI remains a simple and reliable predictor from the clinical point of view.

Carcinoma, Squamous Cell↗
PubMed2002

Fat-suppressed three-dimensional MR angiography technique with elliptical centric view order and no prolonged breath-holding time.

PURPOSE: To determine the appropriate rate of fat-suppression pulses (using spec IR-spectral selective inversion recovery) for fat-suppressed 3D magnetic resonance angiography (MRA) with an elliptical centric view order. MATERIALS AND METHODS: In abdominal 3D fast spoiled gradient echo (fast SPGR) with an elliptical centric view order, the spec IR pulse rate was changed from zero to one every 15 repetitions (in nine steps) in eight volunteers. In the equilibrium phase, abdominal contrast-enhanced 3D MRA was obtained by 3D fast SPGR using an elliptical centric view order without fat-suppression and with two spec IR, and by fat-suppressed 3D fast SPGR with a sequential-centric view order (efgre3D) in 18 cases. Fat and vascular signals were estimated. RESULTS: Although 3D fast SPGR using an elliptical centric view order with spec IR placed every 15 TR and efgre3D effectively decreased fat signals, these sequences lengthened the breath-hold by 4-6 seconds compared with non-fat-suppressed sequence. 3D fast SPGR using an elliptical centric view order and two spec IR reduced the fat signal by 30% and provided good 3D MR angiography without substantial prolongation of breath-hold. CONCLUSION: Two spec IR can be used for generation of partially fat-suppressed abdominal 3D MRA without prolongation of the breath-hold when performing 3D fast SPGR using an elliptical centric view order.

Abdomen↗
PubMed2002

T1-weighted magnetic resonance imaging sequence appropriate for the evaluation of the longitudinal relaxation effect of superparamagnetic iron oxide: a phantom study.

The goal of this study was to determine a T1-weighted magnetic resonance (MR) imaging sequence appropriate for evaluating the longitudinal relaxation effect of superparamagnetic iron oxide (ferumoxides) in a phantom study. An agarose phantom that included various concentrations of ferumoxides (0 - 0.5 mmol/l in 0.05 mmol/l increments) was examined for six types of T1-weighted imaging sequences using a 1.5-T MR unit. Three-dimensional (3D) fast spoiled gradient-echo (SPGR) imaging with a short echo time showed a strong linear correlation between the concentration of ferumoxides and the enhancement ratio. Two-dimensional (2D) fast SPGR imaging showed a high signal-to-noise ratio of the phantom even at low ferumoxides concentrations. These results suggest that 3D fast SPGR imaging is an appropriate technique for the evaluation of the longitudinal relaxation effect of ferumoxides, and that 2D fast SPGR imaging can be useful for evaluating the longitudinal relaxation effect at lower ferumoxides concentrations.

Dextrans↗
PubMed2001

Quantitative and qualitative assessment of reactive hematopoietic bone marrow in aplastic anemia using MR spectroscopy with variable echo times.

OBJECTIVE: To assess quantitative and qualitative differences in water components between normal bone marrow and reactive hematopoietic marrow in aplastic anemia using magnetic resonance (MR) spectroscopy with variable echo times (TEs). DESIGN: Water content, T2 value of the water component, and signal change in water related to TE were assessed in normal bone marrow and reactive hematopoietic bone marrow by a stimulated echo acquisition mode with TEs of 30, 45, 60, and 90 ms. PATIENTS: Six patients with aplastic anemia (13-84 years) and seven normal volunteers (25-38 years) were examined. RESULTS AND CONCLUSION: Reactive hematopoietic marrow showed significantly higher water content than normal bone marrow. The T2 value of water components tended to be longer in reactive hematopoietic marrow. Water signal ratio related to TE was significantly higher in reactive hematopoietic marrow. These results suggest a quantitative and qualitative difference in water components between normal and reactive hematopoietic bone marrow.

Adolescent↗
PubMedDate not supplied

Magnetic resonance imaging of gastrointestinal stromal tumor in the abdomen and pelvis.

This study aimed to evaluate magnetic resonance (MR) imaging appearances of 11 gastrointestinal stromal tumors in the abdomen and pelvis and compared them with some histological findings. Gastrointestinal stromal tumor showed nonhomogeneous signal intensity and included hemorrhage in large tumors. Gastrointestinal stromal tumors showed a wide variety of enhancement, and contrast enhancement of the tumor was consistent with mitosis index as well as the largest diameter of the tumor. Contrast-enhanced MR imaging may be useful in the assessment of tumor activity.

Abdominal Cavity↗