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Biomedical subjects

G D Rubin

Publications and source records attributed to G D Rubin.

At least 73 records · Page 4Linked to original sources
PubMed1995

MR and spiral/helical CT imaging of lower extremity occlusive disease.

Magnetic resonance (MR) angiography and spiral CT angiography are promising new imaging modalities for evaluating patients with lower extremity arterial occlusive disease. Both techniques are less invasive than conventional angiography, and MR angiography has the additional advantages of not requiring iodinated contrast media or ionizing radiation. The basic principles of MR angiography and spiral CT angiography are reviewed with an emphasis on three-dimensional display techniques. This is followed by a discussion of their clinical applicability toward the diagnosis and treatment planning of lower extremity arterial occlusive disease.

Angiography↗
PubMed1995

Assessment of living renal donors with spiral CT.

PURPOSE: To determine whether spiral computed tomography (CT) can be used to evaluate potential living renal donors. MATERIALS AND METHODS: Twelve potential living renal donors underwent spiral CT and conventional arteriography. CT angiography was performed with 30-second spiral acquisition during injection of 150 mL of nonionic iodinated contrast material into an antecubital vein at 5 mL/sec. Five minutes after injection, a frontal abdominal scout projection was obtained to assess the renal collecting system. Results of blinded interpretations of axial CT angiograms, three-dimensional CT angiograms, and conventional arteriograms were correlated with intraoperative findings in 11 cases. RESULTS: Axial and three-dimensional CT angiography were 100% sensitive for identifying seven accessory renal arteries and 14% and 93% sensitive for identifying five prehilar renal artery branches. Renal venous anomalies were confirmed in three patients at surgery. Operative management changed in four of 11 patients who underwent donor nephrectomy. CONCLUSION: Spiral CT holds promise as a single examination for anatomic assessment of living renal donors.

Adult↗
PubMed1995

Detection of ureteral calculi in patients with suspected renal colic: value of reformatted noncontrast helical CT.

OBJECTIVE: The purpose of this study was to determine the value of reformatted noncontrast helical CT in patients with suspected renal colic. We hoped to determine whether this technique might create images acceptable to both radiologists and clinicians and replace our current protocol of sonography and abdominal plain film. SUBJECTS AND METHODS: Thirty-four consecutive patients with signs and symptoms of renal colic were imaged with both noncontrast helical CT and a combination of plain film of the abdomen and renal sonography. Reformatting of the helical CT data was performed on a workstation to create a variety of reformatted displays. The correlative studies were interpreted by separate blinded observers. Clinical data, including the presence of hematuria and the documentation of stone passage or removal, were recorded. RESULTS: Findings on 18 CT examinations were interpreted as positive for the presence of ureteral calculi; 16 of these cases were determined to be true positives on the basis of later-documented passage of a calculus. Thirteen of the 16 cases proved to be positive were interpreted as positive for renal calculi using the combination of abdominal plain film and renal sonography. The most useful CT reformatting technique was curved planar reformatting of the ureters to determine whether a ureteral calculus was present. CONCLUSION: In this study, noncontrast helical CT was a rapid and accurate method for determining the presence of ureteral calculi causing renal colic. The reformatted views produced images similar in appearance to excretory urograms, aiding greatly in communicating with clinicians. Limitations on the technique include the time and equipment necessary for reformatting and the suboptimal quality of reformatted images when little retroperitoneal fat is present.

Adult↗
PubMed1995

Helical (spiral) CT of the retroperitoneum.

Helical CT promises to improve imaging of the retroperitoneum through the elimination of respiratory misregistration and the minimization of partial volume averaging. The speed of acquisition enables the entire abdomen and pelvis to be imaged in less than 2 minutes with standard collimator widths. This is a distinct advantage in critically ill patients, particularly in the case of trauma. Selective intravenously administered contrast enhancement is made possible with helical CT. Rapid scanning allows imaging in an arterial, renal cortical, renal medullary, or delayed collecting system phase. This property of helical CT enables CT angiography to emerge as a powerful minimally invasive alternative to conventional arteriography for imaging the abdominal aorta and its branches. After 4 years of investigating the use of volumetric CT, the clinical settings described herein remain the only clear indications for using helical CT in the kidney and retroperitoneum. These studies took advantage of the single most important feature of helical CT--the elimination of respiratory misregistration. Two broad diagnostic advantages result: (1) the ability to search and characterize a region thoroughly, such as in the evaluation of a small renal mass, or to search for the needle-tip during an interventional procedure; and (2) the ability to create multiplanar and 3-D images that are of sufficient quality to be useful in clinical practice, such as in imaging the vasculature (CT angiogram), and in surgical planning.

Adrenal Gland Diseases↗
PubMed1995

Current status of three-dimensional spiral CT scanning for imaging the vasculature.

Three-dimensional CT angiography is a new modality for minimally invasive vascular imaging. Meticulous attention to technique is critical to optimizing image quality and achieving diagnostic images. In this article, the properties of spiral CT acquisitions, intravenous contrast delivery, and three-dimensional rendering techniques, as they pertain to the optimization of CT angiograms, are discussed. Next, a review of initial investigations into the clinical applicability of CT angiography in the cranium, neck, chest, abdomen, and pelvis is provided. Finally, CT angiography is compared with MR angiography and conventional angiography.

Angiography↗
PubMed1994

Three-dimensional spiral CT angiography of the abdomen.

Spiral CT angiography is a technical innovation in vascular imaging that can produce spectacular three-dimensional reconstructions of the abdominal vessels and organs using modified CT scanning techniques. Rapid volume data acquisition allows contrast material to be imaged in the arterial or venous phase. CT reconstruction in cross-sections avoids superimposition of overlying structures. The combination of these features allows spiral CT angiography to produce extraordinary images of the abdominal vasculature and organs. This review outlines fundamental techniques in spiral CT angiography and summarizes our initial clinical experience at Stanford University Medical Center.

Abdomen↗
PubMed1994

Single breath-hold pulmonary magnetic resonance angiography. Optimization and comparison of three imaging strategies.

RATIONALE AND OBJECTIVES: Ultrafast gradient-recalled-echo techniques for obtaining high-quality pulmonary magnetic resonance angiograms within a single breath-hold were optimized. METHODS: Fourteen subjects were imaged with both the body coil and a phased-array surface coil, using three gradient-recalled-echo pulse sequences: 1) two-dimensional sequential; 2) two-dimensional interleaved; and 3) volumetric acquisitions. Image quality was assessed with varied flip angle, receiver bandwidth, slice thickness/number, and matrix size. Cardiac compensation diminished ghost artifacts in the interleaved sequence. Individual sagittal sections and maximum intensity projections were reviewed. RESULTS: Pulmonary magnetic resonance angiograms acquired with volumetric and two-dimensional interleaved gradient-recalled-echo pulse sequences benefit greatest from intravenous gadolinium and result in greater pulmonary arterial visualization than traditional time-of-flight techniques. Phased-array coils result in improved vessel detection. CONCLUSIONS: High-quality breath-held pulmonary magnetic resonance angiography can be obtained with an intravenous contrast-enhanced gradient-recalled-echo acquisition; however, image quality is dependent on the pulse sequence.

Adult↗
PubMed1994

Three-dimensional helical CT angiography.

CT angiography can accurately depict vascular lesions in less time, with less patient morbidity, and at a lower cost than conventional angiography. Meticulous attention to scan technique is required for achieving diagnostic images. Regardless of the three-dimensional rendering techniques employed, a review of the original axial sections is always required to ensure the detection of any unsuspected parenchymal lesions present and to exclude inaccuracies in segmentation and three-dimensional rendering.

Angiography↗
PubMed1994

Spiral CT of renal artery stenosis: comparison of three-dimensional rendering techniques.

PURPOSE: To evaluate the accuracy of computed tomographic (CT) angiography in the detection of renal artery stenosis (RAS). MATERIALS AND METHODS: CT angiography was performed in 31 patients undergoing conventional renal arteriography. CT angiographic data were reconstructed with shaded surface display (SSD) and maximum-intensity projection (MIP). Stenosis was graded with a four-point scale (grades 0-3). The presence of mural calcification, poststenotic dilatation, and nephrographic abnormalities was also noted. RESULTS: CT angiography depicted all main (n = 62) and accessory (n = 11) renal arteries that were seen at conventional arteriography. MIP CT angiography was 92% sensitive and 83% specific for the detection of grade 2-3 stenoses (> or = 70% stenosis). SSD CT angiography was 59% sensitive and 82% specific for the detection of grade 2-3 stenoses. The accuracy of stenosis grading was 80% with MIP and 55% with SSD CT angiography. Poststenotic dilatation and the presence of an abnormal nephrogram were 85% and 98% specific, respectively. CONCLUSION: CT angiography shows promise in the diagnosis of RAS. The accuracy of CT angiography varies with the three-dimensional rendering technique employed.

Adult↗
PubMed1994

Magnetic resonance imaging and measurement of blood flow.

Blood flow can be shown as a negative image with magnetic resonance spin-echo techniques or as a positive image with gradient-echo techniques. Phase contrast refers to techniques where structures can be seen because of flow-induced phase shifts. These techniques can show the presence (slow flow) and also the direction of flow. Gradient-echo techniques--including phase-contrast versions--can be used with cardiac synchronization to obtain multiple images during the cardiac cycle. These images can be viewed in a movie or cine format to provide dynamic information about blood flow. Blood flow can be measured by using contrast media in boluses or even more elegantly with phase-contrast methods. Clinical applications of flow measurements are growing rapidly. Phase-contrast or gradient-echo techniques can be used to create magnetic resonance angiography, which was first used to study the carotid bifurcation and intracranial circulation and is now being used throughout the body.

Angiography↗
PubMed1993

Three-dimensional spiral CT angiography of the abdomen: initial clinical experience.

Spiral computed tomography (CT) is a new technology that couples continuous tube rotation with continuous table feed. This allows compilation of a data set that has continuous anatomic information without the establishment of arbitrary boundaries at section interfaces as in conventional CT. The unique method of data collection of the spiral scanner has been combined with a dynamic intravenous contrast material bolus to image abdominal vasculature, specifically, the aorta, renal arteries, and splanchnic circulation. Through various techniques of image processing, including surface renderings and maximum-intensity projections, it is possible to obtain excellent anatomic detail of the aorta and its major branches. The authors applied this technique in 15 patients and reliably saw third-order aortic branches as well as third-order splenic-portal venous anatomic detail with remarkable clarity. Pathologic conditions detected include stenotic renal arteries, abdominal aortic dissection, abdominal aortic aneurysm, and celiac bypass graft occlusion.

Abdomen↗
PubMed1993

Three-dimensional spiral computed tomographic angiography: an alternative imaging modality for the abdominal aorta and its branches.

PURPOSE: We sought to apply a new technique of computed tomographic angiography (CTA) to the preoperative and postoperative assessment of the abdominal aorta and its branches. METHODS: After a peripheral intravenous contrast injection, the patient is continuously advanced through a spiral CT scanner, while maintaining a 30-second breath-hold. Thirty-five patients with abdominal aortic, renal, and visceral arterial disease have undergone CTA. RESULTS: Diagnostic three-dimensional images were obtained in patients with aortic aneurysms (n = 9), aortic dissections (n = 4), and mesenteric artery stenoses (n = 4). The technique has also been used to assess vessels after operative reconstruction or endovascular intervention in 18 patients. These preliminary studies have correlated well with conventional arteriographic findings. In aneurysmal disease both the lumen and mural thrombus and associated renal artery stenoses are visualized. The true and false channels of aortic dissections and the perfusion source of the visceral vessels are clearly shown; patency of visceral and renal reconstruction or stent placement are confirmed. CTA is relatively noninvasive and can be completed in less time than conventional angiography with less radiation exposure. CONCLUSIONS: This initial experience suggests that CTA may be a valuable alternative to conventional arteriography in the evaluation of the aorta and its branches.

Adult↗
PubMed1992

Graded compression sonography of abdominal neoplasms mimicking acute appendicitis.

Over a 3-year period nine patients (mean age of 43 years) with acute abdominal pain and unsuspected abdominal neoplasms were referred for graded compression sonography to rule out appendicitis. Six of the nine patients had right lower quadrant neoplasms involving the cecum, terminal ileum, iliacus muscle, or iliac lymph nodes. However, in three patients neoplasm was noted outside the right iliac fossa involving the liver, right kidney, and upper abdominal mesentery. This study underscores the fact that in patients without sonographic evidence of acute appendicitis, a survey of the upper abdomen and right flank should routinely be performed in addition to scanning the right iliac fossa and pelvis. In patients more than 50 years of age neoplasm must also be kept in mind in the differential diagnosis of appendicitis.

Abdominal Neoplasms↗
PubMed1992

CT angiography with spiral CT and maximum intensity projection.

The authors describe a technique for obtaining angiographic images by means of spiral computed tomography (CT), preprocessing of reconstructed three-dimensional sections to suppress bone, and maximum intensity projection. The technique has some limitations, but preliminary results in 48 patients have shown excellent anatomic correlation with conventional angiography in studies of the abdomen, the circle of Willis in the brain, and the extracranial carotid arteries. With continued development and evaluation, CT angiography may prove useful as a screening tool or replacement for conventional angiography in some patients.

Abdomen↗