Biomedical subjects

Tsunehiko Nishimura

Publications and source records attributed to Tsunehiko Nishimura.

113 records · Page 7Linked to original sources

PubMedDate not supplied

Application of pixel truncation to reduce intensity artifacts in myocardial SPECT imaging with Tc-99m tetrofosmin.

BACKGROUND: Technetium 99m-labeled radiopharmaceuticals accumulate in the liver and gallbladder, where they generate intensity artifacts that can result in misdiagnosis of myocardial single photon emission computed tomography (SPECT) images. This study identifies and eliminates factors affecting the magnitude and appearance of intensity artifacts in a gallbladder-heart phantom. METHODS AND RESULTS: The myocardium and background compartments of a phantom were filled with Tc-99m at concentrations of 320 and 26.1 kBq/mL, respectively. A disposable plastic syringe containing 5 mL of Tc-99m as a model of the gallbladder was fixed in a position lateral to the heart phantom. Artifact intensity was determined on SPECT images over a specific activity range in the syringe (28.6, 6.6, and 0.2 MBq/mL). Among 72 projection images, those with maximal heart counts in the region of interest were selected. Counts above and below 110% of the maximal heart count in all projection images were excluded and reconstructed, respectively. At 28.6 and 6.6 MBq/mL, excessive artifacts generated cold pixels immediately around the source, whereas lower activity (0.2 MBq/mL) caused the artifacts to disappear. Truncating the counts in the gallbladder caused the intensity artifacts at specific activities of 28.6 and 6.6 MBq/mL to disappear. CONCLUSIONS: The magnitude and appearance of intensity artifacts depend on contrast between extracardiac activities in the same slices of the heart in myocardial SPECT images with Tc-99m tetrofosmin, and pixel truncation can eliminate them.

Artifacts↗

PubMedDate not supplied

High-resolution imaging of the spine using multidetector-row computed tomography: differentiation between benign and malignant vertebral compression fractures.

OBJECTIVE: The purpose of this study was to investigate the ability of high-resolution computed tomography (CT) images to distinguish between benign and malignant vertebral compression fractures. METHODS: Computed tomography images of 45 benign compression fractures in 40 patients and 33 malignant compression fractures in 33 patients were evaluated. A 16-slice multidetector-row CT scanner was used for data acquisition, and axial images with a slice thickness of 1 mm and sagittal and coronal multiplanar reconstruction images with a slice thickness of 0.7 to 1 mm were used for interpretation. RESULTS: The following findings were significantly more frequent in malignant fractures: destruction of the anterolateral and/or posterior cortex of the vertebral body, destruction of the cancellous bone of the vertebral body, destruction of the end plate, destruction of the pedicle, a paraspinal soft tissue mass, and an epidural mass. The extremely reliable signs of malignancy were destruction of the anterolateral and/or posterior cortex of vertebral body (100% accuracy) and destruction of the cancellous bone of the vertebral body (97.4% accuracy). CONCLUSION: High-resolution CT can provide many useful signs for differentiating between benign and malignant vertebral compression fractures, and its diagnostic ability is sufficient for clinical use.

Aged↗

PubMedDate not supplied

Development of the acetabulum and the acetabular labrum in the normal child: analysis with radial-sequence magnetic resonance imaging.

The degree of acetabular and labral coverage was clarified in children at different positions using radial-sequence magnetic resonance imaging. Scans were performed on 40 hips in 20 normal children (group A, 6-8 years old; group B, 9-11 years old; group C, 12-13 years old) and on 19 hips of 10 healthy adults as controls. The degrees of coverage of the femoral head by acetabulum, acetabular labrum, and both were measured at seven positions at every 15 degrees from anterosuperior 45 degrees via midsuperior to posterosuperior 45 degrees. Coverage of the femoral head by the acetabulum in young children was less than in adults at all positions, but the total coverage including the labrum was greater than in adults. Development of the acetabulum and the acetabular labrum showed differences by position.

Acetabulum↗

PubMedDate not supplied

Iron-induced susceptibility effect at the globus pallidus causes underestimation of flow and volume on dynamic susceptibility contrast-enhanced MR perfusion images.

BACKGROUND AND PURPOSE: Age-related iron accumulation in extrapyramidal nuclei causes T2 shortening, which may result in decreased signal intensity in these areas on MR images. Because the dynamic susceptibility contrast-enhanced technique uses heavily T2*- or T2-weighted images, the iron-induced susceptibility may have direct impact on perfusion imaging. The purpose of this study was to assess the effect of iron-induced susceptibility on the calculated perfusion parameters. The difference of this effect between gradient-echo and spin-echo sequences was also assessed. METHODS: Dynamic susceptibility contrast-enhanced MR perfusion imaging data of 12 patients were used for this study. Perfusion images were obtained using a single shot spin-echo echo-planar imaging sequence in seven patients and a gradient-echo echo-planar imaging sequence in five patients. Region of interest measurements of relative cerebral blood flow, relative cerebral blood volume, and mean transit time were obtained at various parts of the gray matter, including the globus pallidus, putamen, caudate nucleus, thalamus, and cerebral cortex of temporal, frontal, and occipital lobes. The baseline signal intensity on the source images and the magnitude of signal change (DeltaR2* or DeltaR2) were also assessed. RESULTS: The globus pallidus had statistically significantly lower values of relative cerebral blood flow, relative cerebral blood volume, baseline signal intensity, and magnitude of signal change compared with other parts of the gray matter for both gradient-echo and spin-echo sequences (P <.05). Underestimations of these values were more prominent for the gradient-echo than for the spin-echo sequence. Little variance in the measured mean transit time was noted. CONCLUSION: Iron-induced susceptibility effect may lead to underestimation of relative cerebral blood flow and relative cerebral blood volume in the basal ganglia.

Aged↗

PubMedDate not supplied

Percutaneous drainage under real-time computed tomography-fluoroscopy guidance.

BACKGROUND/AIMS: The goal of our study was to assess the use of real-time computed tomography-fluoroscopy guidance for percutaneous drainage of abnormal thoracic, abdominal, and pelvic fluid collections. METHODOLOGY: The subjects were 32 patients who underwent 36 percutaneous computed tomography-fluoroscopy guided thoracic, abdominal, and pelvic drainage procedures to drain abscess (n=29), fluid collection after pancreatitis (n=3), lymphocyst after gynecological surgery (n=3), and the gallbladder transhepatically (n=1) between September 1997 and August 2003. The patient population was 28-86 years old and consisted of 19 men and 13 women. The drainage methods included a Seldinger's technique with a guidewire and serial dilators in every case. The procedures were guided by using a helical computed tomography scanner that provided real-time fluoroscopy reconstruction. RESULTS: Percutaneous drainage under real-time computed tomography-fluoroscopy guidance was successfully performed in every procedure. Real-time computed tomography-fluoroscopy allowed rapid assessment of needle, guidewire, dilator, and catheter placement. The only drainage-induced complication encountered was a subcutaneous hematoma after one procedure (2.8%). No patients had serious complications. The average procedure time was 32 minutes. CONCLUSIONS: Computed tomography-fluoroscopy is a useful method for guiding the accurate and safe drainage of abnormal thoracic, abdominal, and pelvic fluid collections.

Abscess↗