Biomedical subjects

M Amanuma

Publications and source records attributed to M Amanuma.

At least 19 recordsLinked to original sources

PubMed2001

Angiosarcoma of the breast: report of a case and its findings of MRI.

A 67-year-old woman with angiosarcoma of the left breast is presented. Physical findings showed a hard mass in the left breast with skin discoloration and erythema. Mammography showed a high density shadow in the mass without microcalcification and spicula. On ultrasonography, a hypoechoic mass with an ill-defined boundary was detected. On MRI, the tumor had low signal intensity on T1-weighted images, and higher signal intensity on T2-weighted images. MRI with Gd-DTPA images showed higher signal intensity on T1-weighted images with relatively lower intensity in the central area of the tumor. The artery supplying the tumor derived from the left inner thoracic artery and was visualized on three-dimensional dynamic MRI angiography. Initially misdiagnosed as inflammatory breast cancer, an arterial injection of CPA (100 mg) and 5-FU (500 mg) had been performed preoperatively. The definitive diagnosis of angiosarcoma was established by intraoperative frozen section examination. She underwent modified radical mastectomy and is now free of recurrence. This case emphasizes the difficulties in the clinical diagnosis of angiosarcoma of the breast.

Aged↗

PubMed2000

Histopathological analysis of a bladder cancer stalk observed on MRI.

Papillary transitional cell carcinoma of the bladder has a loose connective tissue stalk. For staging of bladder cancer on magnetic resonance imaging (MRI), it is important to clearly separate the cancer from the bladder wall. It is possible to distinguish a stalk from the cancer by the difference of intensity on the using MRI. Sixteen stalks of 20 polypoid bladder tumors on any of the T(2)W(I), dynamic images and delayed enhanced images were demonstrated. Most of the stalks show lower signal intensity than the tumors on T(2)W(I), less enhancement on dynamic images and stronger enhancement on delayed enhanced images. The stalk consisted of fibrous connective tissue, capillary blood vessels, inflammatory cell infiltration and edema. This stalk extended from the bladder wall to the center of the tumor. Some of the superficial muscular bundles were pulled into the stalk. These histopathological findings were compatible with the patterns of signal intensities on MRI. The identification of the stalk of a polypoid tumor may be an important observation to exclude bladder wall invasion by tumor.

Aged↗

PubMed1999

[Bone marrow survey by MRI using a table-moving technique].

The bone marrow of the whole body was imaged by MRI in five normal volunteers. The fast short tau inversion recovery (STIR) sequence and sequential imaging using a moving-table system made sagittal and coronal whole body marrow imaging possible within an examination time of 10 minutes. The images obtained showed high resolution and reflected normal red and yellow marrow distribution in all subjects. Additional abnormalities including humeral bone cyst, hepatic cavernous hemangiomas, and maxillary retention cyst were detected. Fast STIR with the table-moving technique was considered a suitable method for rapid bone marrow survey.

Adult↗

PubMed1999

[Table-moving contrast-enhanced MR angiography of abdominal aortic aneurysm].

Table-moving contrast-enhanced MR angiography (MRA) was performed in 14 cases of abdominal aortic aneurysm to evaluate its clinical usefulness. In all cases, aneurysms were clearly demonstrated and image quality was clinically acceptable. Findings of reconstructed MRA were highly consistent with those of DSA, and thrombosed areas were confirmed on source images. Main aortic branches including renal arteries, common iliac arteries, and internal and external iliac arteries were readily identified on reconstructed MRA and/or source images. Additional findings such as thoracic aortic aneurysm (n = 1), common iliac aneurysm (n = 6), external iliac aneurysm (n = 1), internal iliac aneurysm (n = 1), femoral arterial obstruction (n = 2), and femoral arterial stenosis (n = 4) were also detected. Although table-moving MRA may have disadvantages like reduced blood signal and limited spatial resolution compared with the conventional contrast-enhanced technique, the images that were obtained provided sufficient contrast and resolution for preoperative evaluation. Because abdominal aortic aneurysm is accompanied by various arterial abnormalities in many of the large arteries, table-moving MRA was considered a suitable technique for comprehensive assessment.

Aged↗

PubMed1998

[Detection of recurrent rectal cancer using helical CT with SmartPrep: a new technique for obtaining optimal contrast enhancement].

Seven patients with suspected recurrent rectal cancer underwent Helical CT using SmartPrep. SmartPrep is a software application developed by GE in which the ROI is placed at the desired level of the aorta prior to contrast injection. Using a low-dose continuous scan, the time density curve was obtained instantly, and the optimal timing of scanning was judged from the curve. Four patients who demonstrated intense enhancement at the anastomotic site had local recurrence. No intense enhancement was observed in these areas on conventional delayed CT. Thus, SmartPrep appears to be useful for the accurate diagnosis of recurrent rectal cancer.

Aged↗

PubMed1998

[Normal sternal bone marrow MRI using STIR].

The MR signal of sternal bone marrow was examined in 21 normal volunteers using a sagittal STIR sequence. Craniocaudal phase-encoding with a hand-made positioning device effectively eliminated artifacts due to cardiac pulsation. The sternal bone marrow signal could be classified into three patterns based on the signal distribution. The superior segment of the manubrium showed characteristic age-related changes. This method provided high spatial resolution and excellent bone marrow imaging. Knowledge of a normal marrow signal pattern may be useful for the evaluation of hematological disorders.

Adult↗

PubMed1997

[Application of diffusion-weighted echo planar imaging for diagnosis of small acute and subacute brain ischemic lesions].

The aim of this study was to determine the utility of diffusion-weighted echo planar imaging (DW-EPI) for detecting acute and subacute brain ischemic foci less than 2 cm in size. Thirty patients underwent DW-EPI on a 1.5 T superconducting unit using a SE-EPI sequence with an arbitrary pair of Stejskal-Tanner gradients applied along the imaging axes. DW-EPI demonstrated all the mast recent ischemic lesions as areas of decreased diffusion, providing greater conspicuity and larger size than conventional spin-echo imaging. DW-EPI is a promising method to detect within a subsecond early ischemia and reversible ischemic changes that are not demonstrate on routine spin-echo images.

Acute Disease↗

PubMed1997

[Enhanced 3D subtraction MR angiography of head and neck tumors].

Contrast-enhanced three-dimensional MR angiography (MRA) combined with a subtraction technique was performed in six patients with a solid tumors in the head or neck region. Using the subtraction technique, the contrast-to-noise ratio between the internal carotid artery and fat tissue increased from 18.2 +/- 7.4 to 64.7 +/- 30.8. The MRA findings demonstrated both arteries and enhancing tumors with effective background signal suppression, making tumor extension and relation to the arterial branches more evident. The proposed technique is promising for screening arterial abnormalities of the head and neck in patients with solid tumors.

Head and Neck Neoplasms↗

PubMed1997

[Magnetization transfer MR of cerebrovascular disorders using calculated images].

This study applied a magnetization transfer contrast method to patients with cerebrovascular disorders. A 1.5T superconducting MR unit was used, and magnetization transfer ratio (MTR) images were calculated by evaluating two paired images before and after off-resonance gradient echo pulse sequences. The normal white matter showed the highest MTRs, CSF the lowest, and gray matter, intermediate. Cerebral ischemic patients showed two patterns according to the chronological stage of the affected area. Lesions in the acute and subacute stages revealed higher transfer rates than those in the chronic stage. Patients with cerebral hemorrhage were divided into three groups: the hyperacute group showed a low transfer pattern; the acute group presented inhomogeneous high transfer rates; and the subacute group showed remarkably low transfer rates. In the acute and subacute ischemic stages, increased macromolecules caused higher MTRs than in the chronic stage. In hemorrhagic groups, low MTRs in subacute hemorrhage reflected the transfer of methemoglobin. High MTRs in acute hemorrhage with rich deoxyhemoglobin suggested increased fibrin, plasma, and serum components of macromolecules. The MTC method provided new chronological information on cerebral hemorrhage, adding to that provided by routine MR images.

Adolescent↗

PubMed1995

[Contrast-enhanced 3D MR angiography of the chest and abdomen with breath-holding using phase reordering].

This report presents the feasibility of phase-recordered contrast-enhanced three-dimensional MR angiography in 32 consecutive patients with vascular abnormalities in the chest and abdomen. To suppress motion artifacts due to respiratory corruption, a phase-reordering technique was introduced so that the low frequency components of the phase data were obtained first during the imaging period. Image quality and degree of motion suppression were assessed by four radiologists independently without information on breath-holding time. Abnormalities were detected in 30 cases (93.8%), and their extent was correctly assessed in 28 cases (87.5%). More confident assessment was possible in abnormalities of the pulmonary vessels and thoracic aorta than in those of the abdominal aorta and portal venous system. With phase reordering, more than 20 seconds of breath-holding ensured image quality sufficient to correctly assess the vascular abnormalities. While this technique is easy and requires only single breath-holding, it can provide excellent MRA without slice-to-slice spatial misregistration.

Aortic Aneurysm, Abdominal↗

PubMed1995

[Breath-holding three-dimensional MR imaging: evaluation of phase reordering for motion artifact suppression].

To suppress image degradation due to respiratory corruption during breath holding, a method of reordering of phase encoding was introduced in three-dimensional MR imaging. Without trade-offs in SNR, CNR, and examination time, the method provided a significant reduction of respiratory motion-induced artifacts both in phantom and in vivo experiments. More than twenty seconds of breath holding ensured acceptable image quality regardless of respiratory motion thereafter. Signal intensity change during data acquisition altered the obtained image contrast compared with that of standard sequential linear phase encoding. This technique can be readily implemented on standard two-and three-dimensional pulse sequences and will improve image quality when a patient cannot hold his/her breath during the whole imaging period.

Artifacts↗

PubMed1994

[Three-dimensional MR angiography of aorta with Gd-DTPA infusion and breath-holding].

Using the rapid three-dimensional gradient echo technique (FLASH 18 degrees 10/4) and Gd-DTPA administration, we performed MR angiography (MRA) of the thoracic and abdominal aorta during single or double breath-holding periods. Basic in vitro and in vivo dynamic studies showed that infusion of a relatively low concentration (74 mg Gd/ml) Gd-DTPA solution provided a strong and persistent flow signal for a considerable length of time. Eleven of 12 cases clearly demonstrated MRAs of the aorta and its main branches without respiration-induced motion artifacts, although visualization of secondary and more peripheral branches depended on their size, direction and injection-imaging timing. Although limited spatial resolution and pulsatility-induced ghost artifacts remained as problems to be solved, the ease of this method, short examination time and excellent arteriograms with no need for venous or fat suppression make it clinically acceptable and very promising.

Adult↗

PubMed1994

[Clinical application of three dimensional ultrafast MR imaging to intracerebral traumatic lesions].

We applied a T1-weighted three-dimensional (3D) magnetization-prepared rapid gradient-echo sequence (MPRAGE) for the detection of intracerebral lesions associated with closed head injuries. Thirty-four patients underwent brain MR imaging on a 1.5 Tesla superconducting MR unit. We applied an MPRAGE sequence, together with spin echo (SE) and gradient echo (GRE) sequences, and evaluated the detectability of lesions with each sequence. A total of 100 intracerebral traumatic lesions (33 cortical contusion, 56 diffuse axonal injury, 11 subcortical gray matter injury) were found. Ninety-seven percent of all lesions were detected on MPRAGE images, and 67% on SE and GRE images. The detectability of lesions in each category was 91%, 98%, and 100% on MPRAGE images, and 88%, 54%, and 73% on either SE or GRE images. 3D MPRAGE is a promising method to detect intracerebral traumatic lesions, particularly those associated with diffuse axonal injury, because of its high quality of contrast and spatial resolution and the capability of image reconstruction in any plane.

Adolescent↗

PubMed1994

[Hyaline cartilage delineation of the knee joint using magnetization transfer contrast images].

Using a magnetization transfer contrast method (MTC), we evaluated its clinical feasibility for demonstration of hyaline cartilage of the human knee in five normal subjects. MTC images, obtained from a gradient echo sequence with an off resonance pulse, were compared with those without off resonance pulse. Signal to noise ratio (SNR) and magnetization transfer rate (MTR) were analyzed with respect to hyaline cartilage, muscle, fat, joint fluid and background noise. Also, contrast to noise ratios (CNRs) of cartilage and fluid were compared. MTRs were significantly different between cartilage-muscle group and fat-fluid group. The CNRs of cartilage and fluid were increased on MTC images, showing good contrast separation between hyaline cartilage and joint fluid.

Adolescent↗

PubMed1994

[High resolutional MR angiography of renal arteries with Gd-DTPA infusion and breath-holding].

To obtain high resolutional renal MR angiogram we combined 3D fast scanning technique with Gd-DTPA infusion and surface coil imaging in seven individuals. 1 x 2 x 4 mm spatial resolution provided excellent renal arterial images although thinner slices suffered from decreased signal to noise ratio and ghost artifacts. Twenty seconds interval between injection and data sampling was considered suitable to obtain sufficient signal of the renal arteries. Its easiness, no x-ray irradiation, and capability of repeating study make this technique promising for screening renal arterial diseases.

Adolescent↗

PubMed1992

[2D MR angiography of the aortic aneurysm--effectiveness of oblique saturation pulses for selective angiogram].

2D time-of-flight MR angiography was performed in 6 cases of thoracic aortic aneurysm. Oblique saturation pulses were used to suppress the signals of the pulmonary artery and SVC, providing excellent selective MR aortograms. 3 dimensional extension of the aneurysm and its relation with cervical branches were easily assessed. It could be possible to replace invasive aortography by this technique.

Aorta, Thoracic↗

PubMed1989

[MR imaging of the bone marrow using short TI IR. Part 1--Normal and pathological intensity distribution of the bone marrow].

Normal vertebral bone marrow intensity distribution and its alteration in various anemias were evaluated on short TI IR sequences. Material consists of 73 individuals, 48 normals and 25 anemic patients excluding neoplastic conditions. All normal and reactive hypercellular bone marrow revealed characteristic intensity distribution; marginal high intensity and central low intensity, corresponding well to normal distribution of red can yellow marrows and their physiological or reactive conversion between red and yellow marrows. Aplastic anemia did not reveal normal intensity distribution presumably due to autonomous condition.

Adolescent↗

PubMed1989

[MR imaging of the bone marrow using short TI IR. Part 2--Normal and pathological intensity distribution of the bone marrow].

Bone marrow pathology of hematological neoplasms was evaluated using short TI IR sequences and T2 weighted STIR (IR 1500/100/40, IR 1500/100/80). Material consisted of 49 individuals including 10 leukemias, 5 myelofibroses and 30 multiple myelomas. On IR 1500/100/40, all cases revealed heterogenously or diffusely high intensity. On IR 1500/100/80, both of acute and chronic myelocytic leukemias revealed definite signal decrease, while chronic lymphocytic leukemia, myelofibrosis and multiple myeloma showed no obvious signal decrease.

Adolescent↗