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Biomedical subjects

M Niitsu

Publications and source records attributed to M Niitsu.

64 records · Page 4Linked to original sources

Occurrence of aminopropylhomospermidine and canavalmine in the hamster epididymis.

The Syrian hamster epididymis contains rather high levels of sym-homospermidine, N1-acetylspermidine and N1-acetylspermine in addition to the common polyamines putrescine, spermidine, and spermine. In the present study two other polyamines were identified in adult hamster epididymis by gas chromatography; they are aminopropylhomospermidine [NH2(CH2)3NH(CH2)4NH(CH2)4NH2] and canavalmine [NH2(CH2)4NH(CH2)3NH(CH2)4NH2]. The molar ratio of the former to the latter was about 2:1. This is the first report to show that tetraamines other than spermine are present in mammalian tissues.

Animals↗

Tracking motion with tagged rapid gradient-echo magnetization-prepared MR imaging.

A technique for rapid assessment of tissue motion was developed by combining spatially selective radio-frequency tagging pulses with centric phase-encoding view ordering in a T1-weighted, magnetization-prepared gradient-echo acquisition sequence. This sequence allowed labeling and tracking of tissue motion with single-image acquisition times of less than 3 seconds. Multiple tagged bands 3mm thick were superimposed orthogonal to the imaging plane. Motion in the interval between tagging and the start of image acquisition could then be precisely determined. The technique was evaluated with phantom studies and then applied to human volunteers for assessment of skeletal muscle motion, phonation, and pelvic floor motion.

Humans↗

Hepatic tumors: magnetization transfer MR imaging with gadolinium enhancement.

Thirty patients with 15 hepatocellular carcinomas, 10 metastases, four hemangiomas, and one cholangiocarcinoma underwent magnetic resonance imaging at 1.5 T with T1-weighted, T2-weighted spin-echo (SE) images, gradient-echo (GRE) magnetization transfer (MT) images, and gadolinium-enhanced T1-weighted SE and MT-GRE images. The MT effect and lesion-liver contrast-to-noise ratio (C/N) were calculated and visual assessment (qualitative analysis) performed for unenhanced and enhanced MT-GRE images and enhanced T1-weighted SE images. The C/N values for hepatic adenocarcinomas (seven metastases and one cholangiocarcinoma) and hemangiomas were larger for enhanced MT-GRE images (adenocarcinoma, 8.4 +/- 2.3 [P < .01]; hemangioma 24 +/- 2.1 [P < .05]) than for enhanced GRE images (5.0 +/- 1.9 and 18 +/- 2.7, respectively). These enhancing tumors had the highest scores in the qualitative analysis. Enhanced MT-GRE images showed no advantage for depiction of hepatocellular carcinomas relative to the other images.

Adenocarcinoma↗

High resolution MR imaging of the bilateral hips with dual phased-array coil.

We applied dual-flex coils in a phased-array configuration to obtain high resolution MR images of the bilateral hips and compared the image quality with non-phased-array imaging. Multiple fast spin-echo images of both hips were obtained in a single acquisition. Two consecutive acquisitions with and without phased-array capability were performed in 22 hips and a fluid-filled phantom. The signal-to-noise ratio (S/N) enhancement values were calculated. Subjective image analysis was also obtained from three independent reviewers. High quality MR images were obtained using dual-array coils with a S/N enhancement value of 1.40 for a phantom and 1.83 to 2.22 for subject hips. On subjective analysis, the dual array enhanced delineation of the acetabular labrum, articular cartilage, and retained fluid. The dual array may be of diagnostic value with a higher S/N enhancement and subjective superiority of the images obtained.

Acetabulum↗

MRI of muscle strain injuries.

OBJECTIVE: The purpose of our study was to evaluate (a) the characteristics of muscle strain injuries on MRI and (b) the potential of a frequency-selective fat suppression technique for diagnosing such injuries. MATERIALS AND METHODS: Muscle strain injuries in seven athletes were examined by MRI. Spin echo sequences were obtained with and without fat suppression sequences. The absolute values of the contrast-to-noise (C/N) ratios for lesion versus muscle or fat were then compared for both types of images. RESULTS: We obtained two types of characteristic findings for muscle strain. Lesions of the fascia and adjacent muscles showed a characteristic spray-like or fan-like appearance, extending longitudinally from a shared tendon to the muscle belly in five athletes. This finding was better displayed on coronal images. In contrast, lesions inside a muscle showed a diffuse and inhomogeneous appearance in two athletes. The absolute C/N ratios for lesion versus fat and lesion versus muscle were not significantly different for images with and without fat suppression according to the sign test. However, fat-suppressed images revealed subtle abnormalities that were not seen on conventional images. CONCLUSION: Magnetic resonance can provide detailed information on muscle strain injuries, especially when coronal fat-suppressed images are obtained.

Adolescent↗

Knee extension and flexion: MR delineation of normal and torn anterior cruciate ligaments.

OBJECTIVE: Our goal was to assess the effect of joint position of semiflexed and extended knees in MR delineation of the anterior cruciate ligament (ACL). METHODS: With a mobile knee brace and a flexible surface coil, the knee joint was either fully extended or bent to a semiflexed position (average 45 degrees of flexion) within the magnet bore. Sets of oblique sagittal MR images were obtained for both extended and flexed knee positions. Thirty-two knees with intact ACLs and 43 knees with arthroscopically proven ACL tears were evaluated. Two observers compared paired MR images of both extended and flexed positions and rated them by a relative three point scale. Anatomic correlation in MR images was obtained by a cadaveric knee with incremental flexion. RESULTS: The MR images of flexed knees were more useful than of extended knees in 53% of the case reviews of femoral attachments and 36% of reviews of midportions of normal ACLs. Compared with knee extensions, the MR images for knee flexion provided better clarity in 48% of reviews of disrupted sites and 52% of residual bundles of torn ACLs. Normal ACL appeared taut in the knee extension and lax in semiflexion. CONCLUSION: Compared with MR images of knees in extension, MR images of knees in flexion more clearly delineate the femoral side of the ligament with wider space under the intercondylar roof and with decreased volume-averaging artifacts, providing superior visualization of normal and torn ACLs.

Adolescent↗

Von Meyenburg complexes of the liver: imaging findings.

PURPOSE: Our purpose was to present imaging findings of six cases proven or supposed to be von Meyenburg complexes (VMCs) with a basis of reviewing the pathologic literature and to describe imaging points for the diagnosis of typical VMC along with its differential diagnosis. METHOD: Six cases were diagnosed as VMC of the liver with imaging modalities (one had histopathologic proof). Both ultrasound (US) and CT were available for all cases, and MRI was used for three cases. Follow-up with US, CT and/or MRI was performed in five cases. RESULTS: US detected varying abnormalities of the livers in four cases. CT and MRI revealed multiple or numerous intrahepatic tiny (usually < 5 mm) cystoid lesions in all of the cases. The lesions were scattered throughout the livers, and some of them were located more frequently adjacent to the medium-sized portal veins than to the hepatic veins of similar size on CT. Moreover, some lesions were apparently located in the subcapsular areas (up to the hepatic capsules). They were usually irregular in shape and showed no enhancement but increased in number by approximately 80-150% after administration of intravenous contrast medium. The T2-weighted MR images and MR cholangiopancreatography showed the lesions to be much more apparent and to be more numerous than T1-weighted images did. Follow-up of five cases with imaging modalities did not show remarkable change of the lesions. CONCLUSION: Despite our limited experience, VMC lesions seem to show some CT and MR features different from those of other multiple small hepatic lesions. They presented as multiple or numerous intrahepatic tiny cystoid lesions usually with irregular contour, scattered throughout the liver up to the subcapsular areas, and were detected in far greater number by enhanced CT or T2-weighted MR images than by unenhanced CT or T1-weighted images. They showed no remarkable change on long term follow-up imaging. We propose that a diagnosis of typical VMC could be made after analyzing CT or MR images carefully with good understanding of its pathologic basis, but imaging follow-up is necessary in oncology patients.

Aged↗

MR imaging of Pellegrini-Stieda disease.

OBJECTIVE: To describe the MR imaging of Pellegrini-Stieda disease, a post-traumatic ossification of the medial collateral ligament with typical radiographic findings. METHODS: Coronal and/or axial T2*-weighted field echo and T1-weighted conventional spin echo MR images were obtained with 1.5-Tesla or 0.5-Tesla units. Four patients with radiographic and clinical diagnoses of Pellegrini-Stieda disease were examined. Surgery was performed on one patient, and histopathologic correlation was obtained. RESULTS AND CONCLUSION: Delineating it as a signal void, T2*-weighted MR imaging indicated the precise extent of the osseous fragment in relation to the medial collateral ligament. T1-weighted imaging showed the presence of fatty marrow as a high signal region within the fragment, indicating maturity of the fragment. These findings may help to determine preoperative planning for resection of massive fragments around the ligament. Pellegrini-Stieda disease cannot be considered rare, since it is often encountered in daily MRI examinations.

Adult↗

Fibrous scar in the infrapatellar fat pad after arthroscopy: MR imaging.

PURPOSE: We describe the MR appearance of fibrous scars in the infrapatellar fat pad after arthroscopy. MATERIALS AND METHODS: The subjects were 96 patients who underwent arthroscope-assisted anterior cruciate ligament (ACL) reconstruction and were examined by oblique sagittal MR imaging at different follow-up intervals. Two observers evaluated the characteristics of the fibrous scars in the infrapatellar fat pad. RESULTS: All fibrous scars with low signal intensity were accentuated at the portal and coursed horizontally through the infrapatellar fat pad. The fibrous scar within the fat pad occurred and peaked within 6 months after arthroscopy. It then subsided gradually and had disappeared by one year later in nearly half of the patients. CONCLUSION: Identifying MR imaging characteristics of fibrous scars in the fat pad after arthroscopy may be clinically helpful to differentiate these scars from other abnormalities that involve the infrapatellar fat pad.

Adipose Tissue↗

CT and MRI in detection of intrahepatic portosystemic shunts in patients with liver cirrhosis.

OBJECTIVE: Our goal was to determine the prevalence and anatomic location of intrahepatic portosystemic shunts (IPSs) in patients with hepatic cirrhosis as shown by CT and MRI. MATERIALS AND METHODS: We retrospectively reviewed CT and MR scans of 33 cirrhotic patients who had IPSs. In addition, two series of 100 consecutive CT or MR were reviewed to determine the prevalence of IPSs and the percentage of intrahepatic and extrahepatic paraumbilical veins. RESULTS: Intrahepatic portosystemic shunts were divided into three groups according to the intrahepatic course: paraumbilical shunt between the left portal vein and the paraumbilical vein anterior to the liver (n = 29); inferior vena caval shunt between the posterior branch of the right portal vein and the inferior vena cava (n = 2); and miscellaneous (n = 2). Shunts of the paraumbilical type ran through the medial (n = 23), lateral (n = 3), or both medial and lateral (n = 3) segments of the left lobe of the liver. Twenty-five patients had one shunt, and four had more than one. Six cases were also associated with extrahepatic paraumbilical veins. CONCLUSION: Intrahepatic portosystemic shunts, especially the paraumbilical type, were not infrequently visualized in patients with hepatic cirrhosis.

Adult↗