PubMed Health⌕ Search

Biomedical subjects

M Niitsu

Publications and source records attributed to M Niitsu.

At least 37 records · Page 2Linked to original sources
PubMed1999

Signal intensity changes in anterior cruciate ligament autografts: relation to magnetic field orientation.

RATIONALE AND OBJECTIVES: The purpose of this study was to use magnetic resonance (MR) imaging to investigate the contribution of graft alignment to changes in signal intensity in anterior cruciate ligament (ACL) autografts. MATERIALS AND METHODS: Forty patients who had undergone reconstruction of the ACL with an autograft underwent MR examinations of the knee in extension and flexion. The signal intensity of the intratibial bone tunnel and intraarticular portions of ACL graft were measured, and signal intensity ratios were defined by dividing the mean signal intensity of the graft by the mean signal intensity of the fatty marrow. The angles from the intraarticular and intratibial bone tunnel portions of the graft to the static magnetic field were measured for each signal intensity ratio. The Hotteling T2 test was used to evaluate the differences in signal intensity ratios to the differences in angles from flexion to extension for the intratibial bone tunnel and intraarticular portions of the graft. RESULTS: Significant increases occurred in the signal intensity of the graft and the angle with the change in position from flexion to extension for both the intratibial bone tunnel (P < .01) and intraarticular (P < .01) portions of the graft. Changes in signal intensity ratios were greater than zero, and these values differed significantly for the intraarticular and the intratibial bone tunnel (P < .01) portions of the graft. CONCLUSION: The signal intensity changes of the ACL graft related to changes in its alignment are likely a result of the magic-angle effect.

Adolescent↗
PubMed1999

[MR imaging of the posterolateral aspect of the knee].

The structures of the posterolateral aspect of the knee were evaluated with axial MR images. One hundred twelve knees of clinical cases without posterolateral injury were retrospectively reviewed, and 30 knees of 15 volunteers with no history of knee injury or pain were evaluated. The amount of joint effusion and visualization of the lateral collateral ligament (LCL) and popliteal tendon were classified according to three grades. The LCL and popliteal tendon were identified in 111 clinical cases (99%) and 28 volunteer knees (93%). Visualization of the LCL and popliteal tendon was facilitated in the presence of both joint effusion and fluid collection between the LCL and popliteal tendon. Fluid collection posterior to the femoral attachment of the popliteal tendon was seen in 79 clinical cases (71%) and 20 volunteer knees (67%). Based on cadaveric study, this was considered to be a potential fluid space for communication to the joint space.

Adolescent↗
PubMed1998

Ionspray ionization-mass spectrometric separation and determination of heptafluorobutyryl derivatives of polyamines.

We describe here an application of ionspray ionization-mass spectrometry (IS-MS) for simultaneous determination of putrescine, spermidine, and spermine without the need for coupling with other separation techniques such as high-performance liquid chromatography or capillary electrophoresis. Because it was essential to increase the mass of these compounds to eliminate contaminated low-mass ions, heptafluorobutyryl (HFB) derivatives were chosen. It was found that each HFB-polyamine appeared as a single major cation carrying an ammonium ion in a solution of 50% acetonitrile-water containing 0.5% ammonium acetate at an orifice potential of 20 V. Under these conditions, the three polyamines after addition of 15N-labeled polyamines as internal standards, followed by heptafluorobutylation, were determined simultaneously. It was shown, using a sample injection bulb set between the syringe drive and ionspray probe, that the analysis time for data acquisition was about 3 min and the sensitivity was about 10 fmol. In addition, polyamines in rat liver were determined by this method after simple fractionation with a small column of CM-cellulose with reasonable accuracy and precision. Behaviors of acetylated polyamines were also described, and the results showed that the acetylated polyamines would become additional target compounds in the present method.

Animals↗
PubMed1998

Slightly flexed knee position within a standard knee coil: MR delineation of the anterior cruciate ligament.

The purpose of this study was to assess the value of positioning the knee slightly flexed within a standard MR knee coil in delineation of the anterior cruciate ligament (ACL). Within the confined space of a commercially available knee coil, knee could bend as much as 30 degrees , average 17 degrees of flexion. Sets of oblique sagittal MR images were obtained at both fully extended and slightly flexed positions. Twenty-two normal knees and 18 knees with ACL tears were examined and paired MR images were evaluated by two observers. Compared with knee extension, the MR images for knee flexion provided better clarity in 57 % of reviews of full length of the ACL and 53 % of the femoral attachment. In the extended position the anterior margin of the ligament was obscured due to partial averaging with the intercondylar roof. We recommend examining the knee in an achievable flexed position within the standard knee coil.

Adolescent↗
PubMed1998

Ductectatic mucinous cystic neoplasms of the pancreas: evaluation with MR cholangiopancreatography.

OBJECTIVE: We performed this study to describe the advantages of MR cholangiopancreatography and its findings in revealing ductectatic mucinous cystic neoplasms of the pancreas. CONCLUSION: MR cholangiopancreatography using both projection and source images can reveal characteristic findings of a ductectatic mucinous cystic lesion of the pancreas and show the presence of the communicating duct between the cystic lesion and the main pancreatic duct.

Aged↗
PubMed1998

[Medial collateral ligament of the knee and its surroundings: MRI findings of normal and abnormal structures].

Normal and abnormal structures of the medial corner of the knee were evaluated with coronal and axial MR images. MRI revealed 35 medial collateral ligament (MCL) tears and 61 medial meniscus (MM) tears in 200 consecutive examinations. Just under the MCL, little or no fluid retention was identified between the superficial and deep layers of the MCL or between the MM and MCL in normal knees and in cases of MM tears. At the anterior aspect of the MCL, the deep layer merges with the capsule of the suprapatellar bursa, potentially leaving space for fluid retention. Fluid collection posterior to the MCL was demonstrated in a few cases. Fluid retention with edematous swelling just under the MCL was noted in the cases of MCL tears. MM-MCL distances in the cases of normal structure, MM tears and MCL tears were 2.1 mm, 2.7 mm and 4.7 mm, respectively. The deep layer of the MCL, which was enhanced by the presence of joint fluid, was identified in 71% of cases.

Adult↗
PubMed1997

Multishot echoplanar MR imaging of the female pelvis: comparison with fast spin-echo MR imaging in an initial clinical trial.

OBJECTIVE: The purpose of this study was to apply multishot echoplanar MR imaging (EPI) to the female pelvis and compare image quality with that of fast spin-echo MR imaging. SUBJECTS AND METHODS: Twenty-one patients with suspected pelvic disease and five healthy female volunteers were prospectively examined. MR imaging was obtained using an EPI-capable 1.0-T imager and a pelvic phased-array coil. Axial EPI and fast Spin-echo sequences were obtained at identical image locations in each patient and volunteer. Spin-echo EPI images were obtained using a multishot number of 16. Acquisition time for each EPI sequence was 2 min 10 sec. Fat-suppressed T2-weighted fast spin-echo images were obtained in 2 min 12 sec. Paired EPI and fast spin-echo MR images were independently evaluated by three reviewers. RESULTS: Delineation of the perivaginal and parametrial venous plexus on EPI was rated superior to the fast spin-echo images in 62 (77%) of 81 cases. On EPI, uterine zone anatomy and ovary visualization were judged to be inferior in 44 (56%) of 78 cases and in 18 (33%) of 54 cases, respectively. For delineation of uterine abnormalities, including leiomyoma and adenomyosis, both sequences performed almost equally well. However, ovarian cystic lesions were revealed more precisely by the fast spin-echo sequence. An overall fat-suppression effect was seen on EPI images in 62 (77%) of 81 cases. CONCLUSION: Multishot EPI cannot replace fast spin-echo sequences for imaging the female pelvis; however, because EPI has a potent fat-suppression effect and heavily T2-weighted contrast, EPI sequences can be a valuable adjunct to routine examination.

Echo-Planar Imaging↗
PubMed1997

[High resolution MR imaging of the hip using pelvic phased-array coil].

A pelvic phased-array coil was applied to obtain high resolution MR images of the hip. Three-mm-thick fast spinecho images were obtained in seven hips. Images with a pelvic coil enhanced delineation of acetabular labrum and articular cartilage more clearly than those with a body coil or flexible-surface coil. The use of a pelvic coil in imaging of the hip may be of diagnostic value because of its superior delineation.

Adult↗
PubMed1995

Control of the rate of phosphocreatine resynthesis after exercise in trained and untrained human quadriceps muscles.

We examined the effect of differences in exercise intensity on the time constant (tc) of phosphocreatine (PCr) resynthesis after exercise and the relationships between tc and maximal oxygen uptake (VO2max) in endurance-trained runners (n = 5) and untrained controls (n = 7) (average VO2max = 66.2 and 52.0 ml.min-1.kg-1, respectively). To measure the metabolism of the quadriceps muscle using phosphorus nuclear magnetic resonance spectroscopy, we developed a device which allowed knee extension exercise inside a magnet. All the subjects performed four types of exercise: light, moderate, severe and exhausting. The end-exercise PCr: [PCr+inorganic phosphate (P(i))] ratio decreased significantly with the increase in the exercise intensity (P < 0.01). Although there was little difference in the end-exercise pH, adenosine diphosphate concentration ([ADP]) and the lowest intracellular pH during recovery between light and moderate exercise, significant changes were found at the two higher intensities (P < 0.01). These changes for runners were smaller than those for the controls (P < 0.05). The tc remained constant after light and moderate exercise and then lengthened in proportion to the increase in intensity (P < 0.05). The runners had a lower tc at the same PCr and pH than the controls, particularly at the higher intensity (P < 0.05). There was a significant correlation between tc and [ADP] in light exercise and between tc and both end-exercise PCr and pH in severe and exhausting exercise (P < 0.05). The threshold of changes in pH and tc was a PCr: (PCr+P(i)) ratio of 0.5. There was a significant negative correlation between the VO2max and tc after all levels of exercise (P < 0.05). However, in the controls a significant correlation was found in only light and moderate exercise (P < 0.05). These findings suggest the validity of the use of tc at an end-exercise PCr: (PCr+P(i)) ratio of more than 0.5 as a stable index of muscle oxidative capacity and the correlation between local and general aerobic capacity. Moreover, endurance-trained runners are characterized by the faster PCr resynthesis at the same PCr and intracellular pH.

Adenosine Diphosphate↗
PubMed1995

Fat tissue: relationship between chemical shift and magnetization transfer.

The middle calves of the legs of 25 volunteers (12 men and 13 women, aged 18-25 years), as well as phantoms, were examined with 1.5-T magnetic resonance imaging. Gradient-recalled technique was combined with magnetization transfer contrast (MTC) and chemical shift imaging. Periodic oscillation of the MTC effect in fat tissue with variation of echo time was identified at the frequency corresponding to the water-fat chemical shift difference.

Adipose Tissue↗
PubMed1995

Enzymatic aminopropylation of certain secondary amines.

Two unusual aminopropyl acceptors found in a survey of putrescine binding sites of mammalian spermidine synthase, N-methylputrescine (I) and 4-aminomethylpiperidine (II), were examined for their aminopropyl derivatives. Studies under in vitro incubation conditions suggested that the aminopropyl derivatives of the secondary amine of I and II, N4-methylspermidine (Is) and 1-N-(3-aminopropyl)-4-aminomethylpiperidine (IIs), and of the primary amine of I and II, N8-methylspermidine (Ip) and 4-[N-(3-aminopropyl)aminomethyl]piperidine (IIp), respectively, were biosynthesized by rat spermidine synthase. Studies on the cell culture system of cultured rat hepatoma (HTC) cells treated with alpha-difluoromethylornithine, an ornithine decarboxylase inhibitor, clearly showed the presence of Is and Ip when I was administered, and IIs and IIp when II was administered, with no detection of putrescine or spermidine. These results suggested that mammalian spermidine synthase can transfer the aminopropyl moiety of decarboxylated S-adenosylmethionine to certain secondary amines in living cells.

Animals↗
PubMed1995

[Secondary signs of anterior cruciate ligament tear at MR imaging].

The value of secondary signs of anterior cruciate ligament (ACL) tear was evaluated MR images of 47 knees, 15 with normal, 6 with acutely torn and 26 with chronically torn ACLs confirmed at arthroscopy, were reviewed. Lateral and medial anterior tibial translocations (ATT), posterior cruciate ligament (PCL) bowing ratio and depth of lateral femoral notch (LFN) were measured. The degrees of lateral and medial ATTs and the PCL bowing ratio of the chronically torn ACLs were significantly higher than those of normal ACLs. With cutoff values of 5-mm lateral ATT, 2.5-mm medial ATT and 0.35-PCL bowing ratio, torn ligaments were distinguished from intact ligaments with accuracies of over 80%. Depth of LFN was less sensitive and less accurate. All knees with lateral ATT of 6.4 mm, medial ATT of 3.5 mm, PCL bowing ratio of 0.43 and LFN depth of 1.5 mm or more had torn ACLs. Higher correlations were revealed between lateral ATT and medial ATT, and also between lateral ATT and PCL bowing ratio. Combined criteria of lateral ATT and PCL bowing ratio indicated the highest diagnostic value as a reliable secondary sign of torn ACLs.

Adolescent↗
PubMed1995

[MR imaging features of chronically torn anterior cruciate ligament].

Magnetic resonance (MR) images of 40 knee joints with arthroscopically proved chronic anterior cruciate ligament (ACL) tears were retrospectively evaluated. MRI demonstrated various features of chronic ACL tears: 19 knees revealed with no identifiable ligamentous structure, and 21 had residual ligamentous structures. These pseudoligaments, 14 discontinuous bands and seven continuous bands with elongation, were residual torn ligamentous fibers and/or synovial tissues. All the discontinuous bands were disrupted from the femoral attachment and were likely to traverse the lower intercondylar space. Six disrupted ligaments were attached to the lateral aspect of the posterior cruciate ligament (PCL). Coronal T2-weighted gradient echo images showed better delineation of the disrupted femoral attachment and adhesion to the PCL. A chronic ACL tear with minimal elongation or with PCL attachment at a higher position may occasionally be difficult to distinguish from an intact ligament.

Adolescent↗
PubMed1995

Magnetization transfer contrast on gradient echo MR imaging of the temporomandibular joint.

Thirty-nine temporomandibular joints (TMJ) from 20 patients with suspected internal derangements were imaged by a 1.5 T MR imager. The on-resonance binomial magnetization transfer contrast (MTC) pulse was applied to gradient echo images with a dual receiver coil (9 s/section). With the use of an opening device, a series of sequential images were obtained at increments of mouth opening and closing. The tissue signal intensities with (Ms) and without (Mo) MTC were measured and subjective image analysis was performed. Compared with the standard images, MTC technique provided selective signal suppression of disks. The average of Ms/Mo ratio of the disks (0.56) was lower than that of the retrodiskal pad (0.79) and of the effusion (0.89). With MTC technique, fluid conspicuity was superior to standard image. However, no significant superiority was found in disk definition subjectivity.

Adolescent↗
PubMed1994

[Usefulness of superparamagnetic iron oxide particle (AMI-25) enhanced MR imaging for the diagnosis of liver tumors: comparison with contrast enhanced CT].

The purpose of this study was to clarify the usefulness of SPIO-enhanced MRI in the diagnosis of liver tumors in comparison with contrast-enhanced CT. The subjects were forty patients with 154 nodules in the liver. We compared SPIO-enhanced MRI with contrast-enhanced CT in terms of tumor-liver contrast and detectability of liver tumors. In terms of tumor liver contrast, SPIO-enhanced MRI was equal or superior to contrast-enhanced CT in 82% of cases. In the detectability of liver tumor, SPIO-enhanced MRI detected more tumors than contrast-enhanced CT, especially small tumors. Tumors undetected by SPIO-enhanced MRI that were detected by contrast-enhanced CT and/or plain MRI were adenomatous hyperplasia and inflammatory pseudotumor according to fine needle biopsy. There were no severe complications of SPIO-enhanced MRI. In conclusion, SPIO-enhanced MRI will be more useful than contrast-enhanced CT in the diagnosis of liver tumors. SPIO-enhanced MRI may be a promising diagnostic method for the detection of hepatic tumors, especially small ones.

Adult↗
PubMed1994

Acute change of exercised muscle using magnetization transfer contrast MR imaging.

We evaluated the acute changes in exercised muscle using magnetization transfer contrast (MTC) MR imaging with a short repetition time sequence. Ten volunteers performed supine ankle dorsiflexion exercise. MTC gradient-recalled echo (GRE) images were obtained before and after exercise at 1.5 T. The effect of MTC was assessed by dividing the signal intensity on MTC GRE images by that on conventional GRE images (M(s)/M0). The signal intensity, M(s)/M0 and cross-sectional area of exercised muscle were all greater at 1-2 min after exercise than immediately after exercise. We propose that this additional increase in these parameters after exercise was due to physiological reflow or hyperemia. Since the M(s)/M0 showed a good correlation with free water content in exercised muscle, this ratio may provide a quantitative variable for evaluating dynamic change of water-macromolecule interaction in skeletal muscle.

Adipose Tissue↗