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Biomedical subjects

J S Tsuruda

Publications and source records attributed to J S Tsuruda.

At least 19 recordsLinked to original sources
PubMed1992

Elevated lactate and alkalosis in chronic human brain infarction observed by 1H and 31P MR spectroscopic imaging.

The goal of this study was to investigate lactate and pH distributions in subacutely and chronically infarcted human brains. Magnetic resonance spectroscopic imaging (MRSI) was used to map spatial distributions of 1H and 31P metabolites in 11 nonhemorrhagic subacute to chronic cerebral infarction patients and 11 controls. All six infarcts containing lactate were alkalotic (pHi = 7.20 +/- 0.04 vs. 7.05 +/- 0.01 contralateral, p less than 0.01). This finding of elevated lactate and alkalosis in chronic infarctions does not support the presence of chronic ischemia; however, it is consistent with the presence of phagocytic cells, gliosis, altered buffering mechanisms, and/or luxury perfusion. Total 1H and 31P metabolites were markedly reduced (about 50% on average) in subacute and chronic brain infarctions (p less than 0.01), and N-acetyl aspartate (NAA) was reduced more (approximately 75%) than other metabolites (p less than 0.01). Because NAA is localized in neurons, selective NAA reduction is consistent with pathological findings of a greater loss of neurons than glial cells in chronic infarctions.

Adult↗
PubMed1992

Suspected dural arteriovenous fistula: results with screening MR angiography in seven patients.

Previous studies have shown that spin-echo (SE) magnetic resonance (MR) imaging has been helpful in the assessment of dural arteriovenous fistula (DAVF); however, direct visualization of the fistula site is limited. Thus, conventional plain angiography is required to establish the diagnosis. Because of this limitation, the additional use of MR angiography may improve noninvasive screening for this disorder. Seven patients with DAVFs proved at plain angiography were evaluated with SE MR imaging and with three-dimensional (3D) time-of-flight (TOF) MR angiography. In six of seven cases, 3D TOF MR angiography demonstrated the fistula site. Correlation was good when compared with findings at plain angiography. Occlusion of the dural sinus was found at plain angiography in three of seven patients but was missed at SE imaging in all three. MR angiography also failed to demonstrate sinus occlusion in two of three patients. Arterial feeders could not be seen on SE MR images, but MR angiography improved their depiction. Plain angiography demonstrated abnormal venous drainage into distended cortical veins in three patients, but dilated cortical veins were noted in only two of the patients on both SE MR images and MR angiograms.

Adult↗
PubMed1992

Cytotoxic brain edema: assessment with diffusion-weighted MR imaging.

To determine whether cytotoxic brain edema is associated with a decrease in diffusion, it was induced in rats, in the absence of ischemia, with an established model of acute hyponatremic encephalopathy. Cytotoxic brain edema secondary to acute hyponatremia was induced with intraperitoneal injections of 2.5% dextrose in water and subcutaneous injection of arginine-vasopressin. Coronal spin-echo magnetic resonance (MR) images were obtained with and without strong diffusion-sensitizing gradients before and after induction of acute hyponatremia. The apparent diffusion coefficient (ADC) was measured at two coronal section locations. In hyponatremic rats, the brain ADC was significantly reduced (P = .0153 and .0001) and was positively correlated with increased total brain water content (P = .0011). Plots of ADC versus total brain water showed a statistically significant inverse linear relationship between ADC and increasing brain water at the anterior coronal section location. The results indicate that the ADC may be a sensitive indicator of cytotoxic brain edema and thus may enable quantitative evaluation of such edema with diffusion-weighted MR imaging.

Animals↗
PubMed1991

Diffusion-weighted MR imaging of extraaxial tumors.

The clinical usefulness of the application of spin-echo diffusion-weighted imaging in the evaluation of extraaxial cysts and epidermoid tumors is demonstrated in a series of 15 patients. Apparent diffusion coefficient (ADC) images based on intravoxel incoherent motion (IVIM) were obtained with a maximum gradient b value = 100 s/mm2. Lesion ADC was qualitatively compared to external phantoms. In all cases, epidermoid tumors revealed reduced ADC values similar to that of normal brain tissue. On the other hand, all cysts had ADC similar to the stationary water phantom. Lesion delineation was improved due to the replacement of normal pulsatile (very high ADC) cisternal CSF. Direct quantitative measurements of ADC using this technique may not be possible due to unavoidable motion artifact.

Brain↗
PubMed1991

Noninvasive evaluation of cerebral ischemia. Trends for the 1990s.

A number of diagnostic tools have been developed over the past decade that facilitate the noninvasive evaluation of cerebral ischemia. From duplex Doppler ultrasound to xenon computed tomography and magnetic resonance angiography, a greater trend toward combining both anatomic and function information is anticipated. The methodology, limitations, and current clinical applications of these three diverse techniques, with emphasis on xenon computed tomography and magnetic resonance angiography, are discussed. Both xenon computed tomography and magnetic resonance angiography can be performed on current systems with minimal hardware and software modifications. As a result, standard anatomic and structural imaging can be supplemented with diverse information such as quantitative brain perfusion without and with flow challenging as well as flow mapping and velocity imaging, which approximates conventional x-ray angiography.

Brain↗
PubMed1991

Magnetic resonance imaging and computed tomography of cerebral vascular disease.

Magnetic resonance imaging has emerged as the primary modality in detection and characterization of cerebrovascular lesions. New applications of existing spin-echo and gradient-recalled echo techniques are described. Functional imaging techniques ranging from the characterization of macroscopic proton motion (diffusion-weighted MR imaging), rapid imaging of intravascular contrast transit times (perfusion MR imaging), fast-flow mapping (MR angiography), and in vivo metabolic assessment (MR spectroscopy) are discussed. CT scanning remains important as an initial screening examination, in identifying acute hemorrhage, and in demonstrating blood flow.

Cerebrovascular Disorders↗
PubMed1990

Dural arteriovenous fistulas: evaluation with MR imaging.

The preangiographic diagnosis of cerebral dural arteriovenous fistula (DAVF) can be difficult. The magnetic resonance (MR) images of 12 patients with angiographically proved DAVF were evaluated to characterize the appearance of these lesions and to identify those patients at increased risk for complications. Patients with DAVF demonstrating venous occlusive disease are at higher risk for complications from the arterialized collateral venous system. This venous occlusive disease is demonstrated best at arteriography. The MR imaging appearance of dilated cortical veins without a parenchymal nidus is suggestive of a DAVF with veno-occlusive disease. Eight of the 12 patients in our series demonstrated this finding at angiography. Complications, including infarction and hemorrhage, were identified at MR imaging in eight patients with MR imaging evidence of veno-occlusive disease. At angiography 42% of these complications were not apparent. In one patient with a DAVF draining into an unobstructed right sigmoid sinus, results of MR study were normal. Although patients with DAVF without veno-occlusive disease may have normal findings at MR imaging, DAVF associated with veno-occlusive disease and dilated pial venous drainage can be documented on MR images. This subset of DAVF patients, many of whom were identified only at MR imaging, is at higher risk for complications due to veno-occlusive disease. These patients are believed to require more urgent therapy. MR imaging is useful in the pretherapeutic planning for patients with DAVF.

Adult↗
PubMed1990

Three-dimensional gradient-recalled MR imaging as a screening tool for the diagnosis of cervical radiculopathy.

The purpose of the study was to implement and assess a fast-screening, three-dimensional Fourier transformation (3DFT) MR sequence for the cervical spine. This sequence maintains adequate signal-to-noise and image contrast similar to gradient-recalled echo two-dimensional Fourier transformation (2DFT) imaging. Thirty patients with radiculopathy were examined with 3DFT gradient-recalled echo imaging. The data set consisted of 60 contiguous 1.5- to 2.0-mm-thick axial slices with a total coverage of 9 to 12 cm. In 10 patients, comparison was made with 4-mm-thick axial T1-weighted spin-echo 2DFT or gradient-recalled echo 2DFT studies. With the use of a volume acquisition, adequate signal-to-noise and image contrast similar to T2-weighted gradient-recalled echo 2DFT acquisitions were obtainable. Coverage was improved despite the use of thinner sections without interslice gap. Thin-section 3DFT provided superior detail of acquired foraminal and spinal canal stenosis and disk morphology. Limitations included increased sensitivity to patient motion and "wraparound" artifact in the slice-select direction. Overall, diagnostic confidence was improved with 3DFT owing to the reduction of partial volume artifact. We have adopted this technique as the primary screening method for diagnosing cervical radiculopathy.

Cervical Vertebrae↗
PubMed1990

Diffusion-weighted MR imaging of the brain: value of differentiating between extraaxial cysts and epidermoid tumors.

This study demonstrates the use of diffusion-weighted MR imaging in improving the specificity of the diagnosis of extraaxial brain tumors. Three surgically proved lesions (one arachnoid cyst and two epidermoid tumors) and two nonsurgically proved lesions (arachnoid and ependymal cysts) were evaluated with T1- and T2-weighted spin-echo studies followed by intravoxel incoherent motion (IVIM) MR imaging. The IVIM images of the lesions were displayed as an apparent diffusion coefficient (ADC) image obtained at 0.65 G/cm (maximum gradient b value = 100 sec/mm2) and compared with external oil and water phantoms. The ADC of arachnoid cysts was similar to stationary water whereas the ADC of epidermoid tumors was similar to brain parenchyma, indicating the solid nature and the slower diffusion rate of the epidermoid tumors. Cisternal CSF demonstrated uniformly high ADC, primarily because of bulk flow, which enhanced image contrast. Improved delineation of postsurgical changes was also possible. Our preliminary results show that diffusion-weighted MR imaging can be useful in distinguishing between arachnoid cysts and epidermoid tumors.

Adult↗
PubMed1989

Color Doppler imaging of intracranial vessels in the neonate.

This study was performed to examine the effectiveness of color Doppler imaging (CDI) in demonstrating the neonatal intracranial vessels and altered intracranial flow patterns and to determine the optimal approach in imaging and intracranial vasculature. The study was conducted in two parts. First, 14 neonates were examined with CDI by using a standard approach through the anterior fontanel. Whenever possible, views through the posterior fontanel and the temporal bone were obtained also. The anterior cerebral, M1 segment of the middle cerebral, distal internal carotid, and basilar arteries were demonstrated consistently. Portions of the vertebral distal middle cerebral, and posterior cerebral arteries were frequently visualized. In the second part of the study, we examined 10 neonates who had undergone extracorporeal membrane oxygenation. In this group of patients, CDI was able to demonstrate occlusion of the right internal carotid artery and the reversal of flow through the ipsilateral A1 segment. Increased flow on the contralateral side and in the basilar artery was observed in several patients. The anterior fontanel approach was shown to be the most useful in identifying most of the major intracranial arteries and veins with CDI. In addition, the body weights and gestational ages of the neonates were found to significantly influence the success rate in visualizing the intracranial vasculature.

Basilar Artery↗
PubMed1988

Low-artifact intravascular devices: MR imaging evaluation.

Flow-phantom magnetic resonance (MR) imaging, with use of both spin-echo (SE) and gradient-echo (GRE) techniques at 1.5 T, was performed on the percutaneous Greenfield (beta-III titanium alloy [TMA wire]), Amplatz (MP32-N alloy), and Simon nitinol filters and TMA wire facsimiles of the bird's nest, Gunther, new retrievable, and Amplatz vena caval filters. SE imaging allowed detection of thrombi as small as 5 X 5 mm trapped within the percutaneous Greenfield, Simon nitinol, and TMA-wire facsimile filters; with the MP32-N Amplatz filter, a larger volume of thrombus (10 X 20-mm clots) was necessary for clot detection. GRE imaging allowed detection of intraluminal tilting of the percutaneous Greenfield and facsimile Amplatz (TMA-wire) filters. GRE imaging was useful for demonstrating postfilter turbulence due to clots, which was greatest for the Amplatz filter. Imaging of facsimile vascular devices made of tantalum or TMA wire did not cause the severe "black-hole" MR artifacts typical of the stainless-steel devices. SE and GRE imaging were very useful for determining caval patency in two patients with previously placed Mobin-Uddin filters. Noninvasive MR evaluation of blood vessels in the presence of a variety of low-artifact intravascular devices appears feasible.

Blood Vessel Prosthesis↗
PubMed1988

MR evaluation of large intracranial aneurysms using cine low flip angle gradient-refocused imaging.

MR imaging has proved to be useful in evaluating large intracranial aneurysms. The parent artery and patent lumen can be identified as flow voids and differentiated from thrombus. However, in the presence of slow flow, even-echo rephasing, and motion artifact, increased intraluminal signal may be present, which may be difficult to distinguish from thrombus. Aneurysms are also dynamic lesions and exert pulsatile mass effect on adjacent structures. Further definition of vascular anatomy and physiology may aid in therapeutic planning and assessment. Cine MR is a new technique using a movie loop of sequential GRASS (gradient-recalled acquisition in the steady state) images obtained during various points in the cardiac cycle. The combination of GRASS images and cardiac gating thus allows cinegraphic display of vascular structures. A comparison of this method with routine T1- and T2-weighted MR imaging and angiography was made in a group of 13 patients with intracranial aneurysms greater than 1.5 cm in diameter. Eight of these patients underwent transvascular detachable balloon occlusion. With cine MR, flowing blood has high intensity due to flow-related enhancement. Turbulent and high-velocity flow can be recognized on the basis of signal loss, which occurs during systole. Thrombus demonstrated variable signal intensity, which remained unchanged during the cardiac cycle. Compared with routine MR sequences, there was less image degradation from phase-encoding artifacts and improved visualization of the neck of the aneurysm. Pulsatile mass effect was uniquely assessed. After transvascular embolization, cine MR demonstrated improved conspicuity of acute thrombus and higher contrast between flowing blood and the occlusion balloon when compared with routine MR. Confirmation of flow within the parent vessel, residual aneurysm lumen, and distal arterial branches is possible. If the parent vessel was occluded, cine MR yielded greater information than angiography. Cine MR provides additional anatomic and physiologic data in the evaluation and assessment of therapy of intracranial aneurysms. Information can be obtained that is not available with either routine MR or angiography. The inherent limitations of this new technique include partial-volume artifacts, less than optimal flow-related enhancement or spatial resolution, and poor data acquisition due to cardiac arrhythmias.

Adolescent↗
PubMed1987

Radiation effects on cerebral white matter: MR evaluation.

The purpose of this study was to evaluate the white-matter changes associated with cranial radiation by MR imaging. The MR scans of 95 patients receiving conventional external beam radiation for a wide variety of central nervous system tumors were reviewed. Moderately T2-weighted spin-echo images with a 2000-msec repetition time and 56-msec-echo time were analyzed for white-matter abnormalities without knowledge of the patient's history. These were correlated with radiation dose, port, and time interval since completion of therapy, and then compared with an age-matched control group of 180 patients with nonirradiated, space-occupying, intracranial lesions. Radiation-related lesions were characterized as symmetric, high-signal foci in the periventricular white matter. Relative sparing of the posterior fossa, basal ganglia, and internal capsules was noted. In patients older than 20 years, these changes paralleled those seen in ischemia but were more prevalent (p less than .005). In 25 patients with sequential MR scans, these findings remained stable. In those patients with limited treatment fields, for example, pituitary adenomas, no statistical differences were seen between radiation-treated and nontreated groups. Cerebral white-matter changes that mimic deep white-matter infarction are frequently seen in response to therapeutic radiation. There is a variable incidence of radiation effects, becoming more marked in older patients. MR interpretation must consider the neuropathologic consequences of therapeutic radiation, which include demyelination, microvascular occlusion, and blood-brain barrier breakdown.

Adult↗
PubMed1987

MR sequence parameter optimization: an algorithmic approach.

The MR pulsing sequence is often described by terms such as spatial resolution, signal-to-noise, coverage, acquisition time, and contrast. These might be considered "secondary" parameters because they are not set directly but are instead specified indirectly by setting the "primary" parameters: field of view; projections (phase-encoded or readout); slice thickness and gap; number of excitations; and the sequence parameter times--repetition, echo delay, and inversion. Together, the primary and secondary parameters specify the MR pulsing sequence. Many of these parameters are interrelated such that setting one parameter indirectly affects another. Parameter specification is thus an iterative procedure that involves compromises to achieve an optimum relative to some predefined criteria. In this article, we examine the interrelationships between the primary and secondary parameters that specify the spin-echo pulsing sequence and suggest an algorithmic approach for selecting the best sequence parameters.

Algorithms↗
PubMedDate not supplied

Application of a connected-voxel algorithm to MR angiographic data.

A connected-voxel algorithm (CVA) that improves the contrast and conspicuity of blood vessels in maximum-intensity-projection (MIP) magnetic resonance (MR) angiography is described. Images from a variety of anatomic regions in healthy volunteers were calculated with either an MIP procedure alone or with data that had first been processed with the CVA. A low-signal-intensity threshold is first applied to separate groups of voxels associated with different vessels from one another and to eliminate the contribution from low-intensity stationary material. The remaining voxels are grouped by a connectivity criterion into discrete "objects." Vessels are represented by extended objects, and small objects are discarded. The CVA, therefore, reduces the full three-dimensional data set into a small number of discrete objects. It is a powerful technique that can be used to remove signal from vessels overlying the vessel of interest, to separate objects representing arterial flow from those representing venous flow, to eliminate flow artifact from projection images, and to more completely retain signal within the vascular lumen. This technique has been successfully demonstrated with MR angiography in healthy volunteers.

Algorithms↗
PubMedDate not supplied

Gradient-echo MR imaging of the lumbar spine: comparison with spin-echo technique.

Gradient-echo (GRE) magnetic resonance (MR) imaging has been advocated as the imaging modality of choice for evaluating radiculopathy in the cervical spine. Axial GRE images of the lumbar spine in 50 patients were compared with similar images obtained using spin-echo (SE) technique on a 1.5 T MR system. The SE images were superior to GRE images in the evaluation of the neural foramina, epidural fat, and disk herniation. The GRE images obtained were inadequate for lumbar spine imaging due to an unacceptable level of chemical shift artifacts. The GRE technique does provide the advantages of rapid acquisition of T2* images and decreased motion artifact. Axial GRE images may play an increasingly important role in lumbar spine imaging with continued changes in software and improvements in technology.

Adolescent↗
PubMedDate not supplied

Three-dimensional time-of-flight MR angiography in the evaluation of cerebral aneurysms.

We review our preliminary experience with the use of three-dimensional (3D) time-of-flight (TOF) magnetic resonance (MR) angiography (MRA) in the assessment of intra- and extracranial aneurysms. Six patients were examined: Five had intracranial aneurysms and one had a cervical carotid pseudoaneurysm. A 3D rephased gradient recalled echo pulse sequence and maximum intensity projection (MIP) reconstruction algorithm were used. Magnetic resonance angiography, spin echo MR, and conventional angiography were retrospectively reviewed with specific regard to individual vessel visualization, aneurysm depiction, and presence of artifact related to acquisition techniques or MIP reconstruction. All aneurysms were detected on MRA, and anatomical correlation with conventional angiography was excellent. Significant problems included loss of visualization of small vessels, intraluminal signal loss in large vessels, subacute thrombus simulating flow on MIP reconstructions, and limited projections obtainable with MIP techniques. Adequate MRA assessment of aneurysms can be obtained using a combination of T1-weighted spin echo images and 3D TOF MRA. Review of all components of the MRA is required. MRA may be useful in screening asymptomatic patients for intracranial aneurysms as well as in the follow-up of patients treated with balloon occlusion.

Adult↗