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H D Sostman

Publications and source records attributed to H D Sostman.

At least 19 recordsLinked to original sources
PubMed1992

Thick-section, single breath-hold magnetic resonance pulmonary angiography.

RATIONALE AND OBJECTIVES: Approaches to performing magnetic resonance angiography (MRA) of the pulmonary vasculature are described using very fast (repetition time [TR] less than 13 mseconds) radiofrequency (rf)-spoiled, gradient-recalled pulse sequences and the standard quadrature body imaging coil of a commercial 1.5-T MR imaging system. METHODS AND RESULTS: Signal-to-noise (SNR) is improved by signal averaging (Nex greater than or equal to 4) in a two-dimensional, single thick-section approach and by volume acquisition (Nex = 1) in a three-dimensional approach. Blood signal loss is minimized by using short, asymmetric echoes (echo time [TE] less than or equal to 2.7 mseconds). Respiratory motion is eliminated by keeping the scan time short enough (approximately 15 seconds) for image acquisition within a single breath-hold. Cardiac motion artifacts are reduced with section orientations that avoid intersecting the heart and/or use of small flip angle (alpha less than or equal to 25 degrees). CONCLUSIONS: Images of healthy volunteers showed that while single thick sections have superior SNR, the three-dimensional approach appears to produce better visualization of the peripheral vascular segments and offers improved ability to process the images to remove overlapping structures.

Adult↗
PubMed1992

Renal carcinoma: detection of venous extension with gradient-echo MR imaging.

Magnetic resonance (MR) imaging has been proposed as a noninvasive alternative to vena cavography and computed tomography for the detection of venous extension of renal adenocarcinoma. However, spin-echo MR images may be compromised by the presence of flow-related artifacts, extrinsic compression, and respiratory or cardiac motion artifacts. Use of gradient-recalled echo (GRE) sequences is advantageous for imaging of vascular structures. To investigate the detection of vascular extension of tumor with the GRE technique, findings in the preoperative GRE MR images of 26 patients with renal adenocarcinoma were compared with findings at surgery and pathologic examination. Vena cava thrombus was correctly identified in 13 of 13 patients (100%). Renal vein thrombus was correctly identified in 23 of 26 patients (88%), and right atrial thrombus was correctly identified in four of five patients (80%). Use of GRE sequences allows accurate assessment of vascular structures that is sufficient for surgical planning.

Adult↗
PubMed1992

Pulmonary vasculature: single breath-hold MR imaging with phased-array coils.

The authors obtained magnetic resonance images of the pulmonary vasculature with reduced artifacts caused by cardiac and respiratory motion by acquiring a series of moderately thin sections in a single breath-hold with an ultrafast gradient-echo pulse sequence. The series of two-dimensional images was postprocessed with a maximum-intensity projection algorithm. Time-of-flight inflow enhancement increased the signal intensity of arteries and veins while radiofrequency phase spoiling produced limited stationary spin suppression of the chest wall. Moderately thin (8-mm) section thicknesses were used to attain the resolution necessary to visualize smaller pulmonary vascular segments up to the chest wall while the number of acquired sections was minimized. Because the body coil did not provide an adequate signal-to-noise ratio (S/N) for a single excitation and thin-section acquisitions, phased-array coils covering either the right or left lung were used to single breath-holds prevented the misregistration and blurring that occurred in examinations performed with multiple breath-holds.

Humans↗
PubMed1992

Prospective validation of the stripe sign in ventilation-perfusion scintigraphy.

The data base of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) was used to test the accuracy of the stripe sign for the exclusion of embolic perfusion defects on lung scintigrams. Lung scan readings showed the presence and location of this sign in 50 (4.7%) of 1,064 patients. Perfusion defects showing the stripe sign were not associated with pulmonary embolism in the same lung zone (upper, middle, or lower third of each lung) in 93% (79 of 85) of instances. Thirty-eight percent (n = 32) of lung zones with the stripe sign had associated chest radiographic abnormalities, and 69% (n = 59) had ventilation scan abnormalities. Formulation of the scan diagnosis according to PIOPED criteria showed fewer indeterminate readings in patients with the stripe sign and without pulmonary embolism when the stripe sign was used. Use of the sign changed diagnosis in less than 1% of the total population, however, because of its low overall prevalence. The stripe sign is a useful adjunct to standard criteria in the interpretation of pulmonary scintigrams for evaluation of suspected acute pulmonary embolism.

Humans↗
PubMed1992

Magnetic resonance imaging--cardiac ejection fraction measurements. Phantom study comparing four different methods.

The accuracy of cardiac ejection fraction (EF) measurements with thin, contiguous cine-magnetic resonance imaging (MR) sections is well established. Still, faster imaging and measurement techniques would be desirable. The authors evaluated the accuracy of four different MR EF measurements methods in a biventricular, anthropomorphic, foam-latex rubber phantom which was connected via noncompliant fluid-filled tubing to a pulsatile flow pump. Nine contiguous 10 mm cine-MR sections (TR/TE, 25/13; flip angle, 45 degrees) were obtained through the heart in long and short cardiac axes at 16 frames per cardiac cycle at a pump rate of 60 beats/minute. EF measurements were based on either the multi-slice summation technique (nine contiguous 10-mm sections versus four 10-mm sections spaced 10 mm apart) or the area-length method (single largest long section versus combination of largest long- and short-axis section). Three replications were performed for each of the tested EFs (40.8%, 29.4%, and 13.4%), which were compared with actual EFs. EF measurements based on contiguous 1-cm sections correlated best with the actual EFs. Average relative errors ranged from 3.2% to 6.0%. EF measurements based on every other section were less accurate; average relative errors were between 5.2% and 10.2%. Single and biplane area-length algorithm EF measurements were significantly less accurate; average relative errors were as high as 59%. EF measurements based on multi-slice summation are more accurate than those based on the area-length algorithm. Contiguous 1-cm section acquisitions are most accurate and most time consuming. With slight decrease of accuracy, acquisition and processing times can be halved by skipping every other slice.

Humans↗
PubMed1991

Evaluation of BA1112 rhabdomyosarcoma oxygenation with microelectrodes, optical spectrophotometry, radiosensitivity, and magnetic resonance spectroscopy.

We studied tumor tissue oxygenation in the BA1112 rhabdomyosarcoma using micro-electrode pO2 measurements, optical spectrophotometry, analyses of cell survival after irradiation, and 31P magnetic resonance spectroscopy (MRS). Studies were carried out in WAG/Rij/Y rats breathing normoxic, hypoxic, and hyperoxic gas mixtures with and without iv administration of perfluorochemical. Significant changes in tissue oxygenation and metabolic status were found when pO2 values, optical measurements of hemoglobin saturation and cytochrome a, a3 reduction-oxidation, radiation cell survival determinations, and MRS measurements of phosphometabolite ratios were obtained in rats breathing different gas mixtures. Inhalation of 100% O2 caused increases in tumor pO2, hemoglobin saturation, cytochrome a, a3 oxidation, tumor radiosensitivity, and PCr/Pi, NTP/Pi, and PDE/Pi ratios. Such changes were augmented by pretreatment with iv perfluorochemicals. Inhalation of hypoxic gas mixtures resulted in reductions in the above parameters. These results indicate that tissue oxygenation can be manipulated reproducibly in the BA1112 rhabdomyosarcoma and suggest that 31P MRS can be used to monitor changes in tumor oxygenation in this model system.

Animals↗
PubMed1991

Evaluation of acute renal failure with magnetic resonance imaging using gradient-echo and Gd-DTPA.

Detection of acute renal failure (ARF) using fast-scan magnetic resonance imaging (MRI) with Gd-DTPA was studied in a dog model. ARF was produced in five dogs by infusion of norepinephrine (0.75 micrograms/kg/min) into the renal arteries for 40 minutes. MRI was performed 1 hour later and compared with baseline (pre-ARF) MRI. There was no significant difference in the ratios of signal intensity-vs.-time curves from 0 to 35 seconds after injection of Gd-DTPA. However, a difference between the outer and inner medulla was significant in the time period of 5 to 20 minutes after Gd-DTPA injection. These later signal intensity differences by fast-scan (gradient-echo) technique may be useful in the evaluation of ARF.

Acute Kidney Injury↗
PubMed1991

Cine phase-contrast magnetic resonance imaging for analysis of flow phenomena in experimental aortic dissection.

Using a 1.5 T magnetic resonance imaging (MRI) system, cine phase-contrast and magnitude images were obtained in three phantoms that simulated different anatomic configurations of aortic dissection. The dissection phantoms were made of compliant materials, and pulsatile flow was used in all experiments. Phantoms differed only in the location of the fenestration between the true and false lumens (I: an upstream "entry" only, II: both upstream "entry" and downstream "re-entry," and III: a downstream "entry" only). Flow jets, flap motion, and wave propagation were clearly visualized in cine MR images of each phantom, and quantitatively analyzed with reference to the stimulated cardiac cycle of the pump. Flow in the false lumen was always bidirectional. Upstream and downstream flow waves collided and dispersed within the false lumen. Flow through the false lumen was the same in phantoms I and II, and least in phantom III. The average area of the true lumen was largest in phantom III and smallest in I. Phantom I had the highest overall flow rate in the false lumen and greatest change in false lumen size during the cardiac cycle, while the downstream "entry" phantom had the lowest of both parameters. Flow phenomena in aortic dissections can be studied by cine phase-contrast MRI.

Aortic Dissection↗
PubMed1991

Status of clinical MR evaluations 1985-1988: baseline and design for further assessments.

The authors modified the methods used by Cooper et al (JAMA 1988; 259:3277-3280) to describe magnetic resonance (MR) clinical research during 1985-1988 in an objective manner. To avoid other shortcomings faced by Cooper et al, the authors randomly sampled 500 articles and obtained estimates of probable errors. Excluding case reports, all 40 of the studies with human subjects provided some evidence of prior research planning, which compares favorably with the 22% found by Cooper et al. Use of a standard for truth was similar between the data sets. Observer blinding, random ordering of procedures, and assessment of interobserver variability continued to be uncommon. Most studies provided only minimal statistical information. The work of these authors provides a study design and the baseline needed for future assessments of MR imaging evaluations.

Animals↗
PubMed1991

1990 ARRS Executive Council Award. Renal transplant rejection: diagnosis with 31P MR spectroscopy.

We evaluated the role of 31P MR spectroscopy in the diagnosis of renal transplant allograft dysfunction. Thirty-six 31P MR spectroscopy examinations were prospectively performed in 35 patients with renal allografts. The study was performed in two phases. In the first phase, 12 transplant recipients with normal graft function were studied as normal controls. During phase two, 24 31P MR spectroscopy studies were performed in patients at the time of renal transplant biopsy for allograft dysfunction. Twenty-one of these studies were technically adequate. Pathologic analysis of the biopsy specimens showed evidence of allograft rejection in 14 and no rejection in seven. Various phosphorus metabolite ratios were calculated for each patient, including phosphodiesters/phosphomonoesters (PDE/PME), phosphomonoesters/inorganic phosphate (PME/Pi), and inorganic phosphate/adenosine triphosphate (Pi/ATP). The PDE/PME and Pi/ATP ratios in the allografts with rejection differed significantly from the corresponding metabolite ratios in patients without rejection (p = .017 and p = .024, respectively). A PDE/PME ratio exceeding 0.8 had a sensitivity of 100% and specificity of 86% for predicting rejection. A Pi/ATP ratio greater than 0.6 had a sensitivity of 72% and a specificity of 86% for predicting rejection. We conclude that 31P MR spectroscopy may be useful as a noninvasive method for evaluating renal metabolism during episodes of transplant allograft dysfunction.

Adenosine Triphosphate↗
PubMed1991

Imaging of the renal arteries: value of MR angiography.

We compared the efficacy of MR angiography with that of conventional angiography for visualizing the renal arteries and detecting renovascular disease. Thirty-three MR angiographic studies, consisting of axial two-dimensional (2-D) phase-contrast, coronal 2-D phase-contrast, and coronal 2-D time-of-flight acquisitions, were performed within 48 hr of conventional arteriography. The studies were done to evaluate possible renovascular hypertension (n = 25) or potential donor nephrectomy (n = 8). The three MR image sets were interpreted independently, in random order by three observers, with regard to the number of renal arteries, degree of vessel visualization, arteriovenous overlap, and presence of renovascular disease. A fourth interpretation was based on the combined axial and coronal phase-contrast image sets. Evaluation was limited to the proximal 35 mm of each renal artery. Renal artery visualization and detection of renovascular disease were more complete with coronal phase-contrast (80% sensitivity, 91% specificity) than with time-of-flight (53% sensitivity, 97% specificity) images. Combined axial and coronal phase-contrast images permitted visualization of the proximal 35 mm of all dominant renal arteries and detection of 13 of 15 stenoses (87% sensitivity, 97% specificity). Our data suggest that biplanar MR angiography has considerable potential as a noninvasive screening technique for the evaluation of renovascular disease.

Angiography↗
PubMed1991

An analysis of the inter-relationships among multiple bronchoalveolar lavage and serum determinations, physiologic tests, and clinical disease activity in patients with sarcoidosis.

Analysis of epithelial lining fluid from the lungs of patients with sarcoidosis frequently suggests the presence of an alveolitis. Several markers of this inflammatory response were quantitated in bronchoalveolar lavage fluid and serum from 45 non-smoking patients with sarcoidosis. All markers were elevated significantly compared to those from 19 normal controls. The degree of statistical correlation among all data was assessed. Pulmonary function tests, 67Gallium lung scans, and a clinical index of disease activity also were quantitated. When patients were grouped by the number of abnormal BAL lavage and serum markers, those patients with elevated values of five or more of these markers had significantly worse clinical disease and lower carbon monoxide diffusing capacities. These results indicate that pulmonary sarcoidosis is an immunologically heterogeneous disease and that measurement of several markers of disease activity may be required to accurately estimate the activity of the lung disease.

Adult↗
PubMed1991

Clinical application of PET for the evaluation of brain tumors.

The combination of FDG and PET has demonstrated clinical utility in the evaluation of patients with brain tumors. At the time of diagnosis, FDG PET provides information concerning the degree of malignancy and patient prognosis. After therapy, FDG PET is able to assess persistence of tumor, determine degree of malignancy, monitor progression, differentiate recurrence from necrosis, and assess prognosis. Other studies using PET provide information that may be clinically useful. Determination of tumor blood flow and permeability of the blood-brain barrier may help in the selection of appropriate therapy. Amino acid imaging using 11C-methionine is being evaluated in patients with brain tumors and provides different information than FDG imaging.

Brain Neoplasms↗
PubMed1990

MR imaging of experimental and clinical thrombi at 1.5 T.

We have previously reported that the T1 and T2 of experimental clots at 0.47 T varies considerably depending upon the method used in their preparation. However, these studies, while relevant to midfield imaging, may not reflect accurately the behavior of such thrombi at higher field strengths. Accordingly, we studied the T1 and T2 at 1.5 T of experimental thrombi prepared by several methods and compared these results with the relaxation times of clinical deep venous thrombi measured in situ in patients. The relationship between the T2 values for the different clot preparation methods was different at 1.5 T than at 0.47 T. The combined use of thrombin and epsilon-amino caproic acid produced thrombi with T1 and T2 indistinguishable from clinical deep venous thrombi.

Aminocaproic Acid↗
PubMed1990

Effects of cell membrane disruption on the relaxation rates of blood and clot with various methemoglobin concentrations.

The magnetic resonance imaging (MRI) characteristics of hemorrhage and clotted blood change with age. The effects of methemoglobin and cell membrane lysis, factors which in part may underlie this evolution of imaging characteristics, were studied using clotted and heparinized dog blood at various methemoglobin concentrations. Cell lysis did not alter the longitudinal relaxation rate (1/T1) in clotted or unclotted samples. Membrane lysis altered significantly the transverse relaxation rate (1/T2) in both clotted and unclotted samples. Lysed samples of oxygenated blood at 0% methemoglobin had significantly higher T2 values than intact samples. At 0% methemoglobin, clotted samples had slightly but significantly shorter relaxation times than unclotted samples. Within the samples studied, large changes in the state of oxygenation and methemoglobin content were observed in less than 24 h. Such changes necessitate frequent monitoring of these parameters if serial studies are to be done.

Animals↗