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Biomedical subjects

R C Brasch

Publications and source records attributed to R C Brasch.

At least 163 records · Page 9Linked to original sources
PubMed1984

Acute myocardial ischemia: magnetic resonance contrast enhancement with gadolinium-DTPA.

Gadolinium-DTPA (Gd-DTPA) was used to improve the diagnostic utility of magnetic resonance (MR) in detecting early ischemia, before the onset of infarction. Following one minute of left anterior descending coronary artery occlusion, 9 dogs were intravenously injected with either 0.5 mM/kg of Gd-DTPA (6 dogs) or normal saline (3 dogs). One more minute was allowed for perfusion of injectate prior to cardiectomy and MR imaging of the ex situ heart. There was no visible difference in intensity or alterations in magnetic relaxation times between normal and ischemic myocardium in the control (saline-injected) animals. The Gd-DTPA-injected dogs had a well-defined segment of high intensity representing the ischemic myocardium in the anterior wall of the left ventricle, due to significant T2 relaxation rate enhancement in the adjacent normal myocardium. Both T1 and T2 were significantly (p less than 0.01) shortened in the normal myocardium of the Gd-DTPA animals, but relatively greater T2 relaxation rate enhancement resulted in reduced intensity of normal myocardium, thus increasing contrast with ischemic myocardium. As a result of the significant shortening of T1 and T2 in the normal myocardium relative to the ischemic myocardium, improved delineation of the ischemic segment could be obtained using calculated T1 and T2 images. It is concluded that Gd-DTPA has the potential to expand the sensitivity and diagnostic utility of MR in the study of occlusive coronary artery disease.

Animals↗
PubMed1984

Effect of gadolinium-DTPA on the magnetic relaxation times of normal and infarcted myocardium.

Acute myocardial infarctions were produced in 11 dogs by ligation of the left anterior descending coronary artery. Twenty-four hours after ligation, 0.35 millimoles per kilogram of Gd-DTPA was injected intravenously, followed by cardiectomy either 90 seconds (3 dogs) or 5 minutes (5 dogs) later. The remaining 3 dogs had cardiectomy without injection of Gd-DTPA at 24 hours after coronary occlusion. The 3 dogs that did not receive Gd-DTPA had longer T1 and T2 relaxation times in infarcted myocardium than in normal myocardium, as measured by a 10.7-MHz magnetic resonance (MR) spectrometer. The T1 and T2 relaxation times of normal myocardium at 90 seconds postinjection of Gd-DTPA were significantly shorter (p less than 0.05) than those of the normal myocardium of animals that did not receive Gd-DTPA. At five minutes postinjection, significantly (p less than 0.01) greater T1 shortening was exhibited in the infarcted myocardium compared with adjacent normal myocardium in the dogs injected with Gd-DTPA. Thus, Gd-DTPA has differential and time-varying effects on relaxation times of normal and infarcted myocardium.

Animals↗
PubMed1984

Magnetic resonance imaging of vascular lesions in children. Assessment of flow patterns.

Ten children aged 1 week to 13 years with 12 vascular abnormalities were examined with magnetic resonance imaging (MRI) and other imaging modalities. MRI was the only single non-invasive modality that demonstrated all lesions and their internal structures. The vascular nature of 3 hemangiomas could not be established with MRI alone. No marked differences in MRI appearance was seen in 5 cases with vascular tumors compared with 5 cases with other vascular abnormalities. The status of the blood in the vascular lesions as flowing fast, slow, or not at all was successfully assessed in 9 of the 12 lesions.

Aortic Aneurysm↗
PubMed1984

Characteristics of gadolinium-DTPA complex: a potential NMR contrast agent.

Chelation of the rare-earth element gadolinium (Gd) with diethylenetriaminepentaacetic acid (DTPA) results in a strongly paramagnetic, stable complex that is well tolerated in animals. The strongly paramagnetic gadolinium complex reduces hydrogen-proton relaxation times even in low concentrations (less than 0.01 mmol/L). The pharmacokinetic behavior of intravenously delivered Gd-DTPA is similar to the well known iodinated contrast agents used in urography and angiography; excretion is predominantly through the kidneys with greater than 90% recovery in 24 hr. The intravenous LD50 of the meglumine salt of Gd-DTPA is 10 mmol/kg for the rat; in vivo there is no evidence of dissociation of the gadolinium ion from the DTPA ligand. The combination of strong proton relaxation, in-vivo stability, rapid urinary excretion, and high tolerance favors the further development and the potential clinical application of gadolinium-DTPA as a contrast enhancer in magnetic resonance imaging.

Animals↗
PubMed1984

Contrast-enhanced NMR imaging: animal studies using gadolinium-DTPA complex.

Gadolinium (Gd)-DTPA complex was assessed as a nuclear magnetic resonance (NMR) contrast-enhancing agent by experimentally imaging normal and diseased animals. After intravenous injection, Gd-DTPA, a strongly paramagnetic complex by virtue of unpaired electrons, was rapidly excreted into the urine of rats, producing an easily observable contrast enhancement on NMR images in kidney parenchyma and urine. Spin-echo intensity of urine within the renal pelvis increased from 2263 to 4414 units; intensity of renal parenchyma increased from 2901 to 3893 after administration of 0.1 mmol/kg Gd-DTPA. Sterile soft-tissue abscesses demonstrated an obvious rim pattern of enhancement. A focus of radiation-induced brain damage in a canine model was only faintly detectable on spin-echo NMR images before contrast administration; after 0.5 mmol/kg Gd-DTPA administration, the lesion intensity increased from 3867 to 5590. In comparison, the normal brain with an intact blood-brain barrier remained unchanged in NMR characterization. Gd-DTPA is a promising new NMR contrast enhancer for the clinical assessment of renal function, of inflammatory lesions, and of focal disruption of the blood-brain barrier.

Abscess↗
PubMed1984

Paramagnetic pharmaceuticals for magnetic resonance imaging.

Complexes of paramagnetic ions that are tissue-, organ- or tumor-specific will supplement routine magnetic resonance imaging, help assess organ perfusion, and in some cases assess specific organ function. Studies are described in animals and man and the results suggest that dilute iron solutions may be useful for contrast-enhancement of the gastrointestinal tract; that ferrioxamine B, a stable ferric iron complex, appears to permit identification of focal blood-brain-barrier defects and to assess renal excretory function; and that gadolinium-DTPA can produce contrast-enhancement of a variety of lesions. In addition, gadolinium-DTPA can detect a breakdown in the blood-brain-barrier and can delineate functioning myocardium in the setting of acute ischemia.

Abdomen↗
PubMed1983

Clinical nuclear magnetic resonance imaging of the body.

NMR promises great advances in diagnosis and has delivered so much already that it is expected that in the future it will replace many applications of the currently used imaging modalities. Although x-ray computed tomography is continuing to advance in speed of scanning and resolving power, NMR will most likely soon eliminate its use in many studies of the central nervous system and also in many other areas of the body. The promise of combining topical spectroscopy with imaging is also exciting and should provide further information about metabolic processes of various organs. Progress in NMR is so rapid and the future is so bright that one of the great problems will be to develop a new breed of radiologists who are versatile in biochemistry, mathematics, and computers, as well as competent in morphologic anatomy and pathologic physiology. As time goes on, advances in NMR will be achieved only by teams of clinical and basic scientists encompassing multiple disciplines.

Aortic Aneurysm↗
PubMed1983

Work in progress: methods of contrast enhancement for NMR imaging and potential applications. A subject review.

Contrast-enhancing pharmaceuticals and manipulation of the physical properties of tissue may extend the diagnostic usefulness of nuclear magnetic resonance (NMR) imaging. Potential applications of contrast enhancers include differentiation of isomagnetic tissues, direct evaluation of tissue function, evaluation of metabolic pathways, and measurement of tissue perfusion. Numerous means of enhancing NMR contrast are available, but many, such as manipulation of tissue viscosity or temperature, are not clinically feasible. Changing the chemical composition of tissue, and particularly the use of paramagnetic pharmaceuticals, appears to be more advantageous. Nitroxide stable free radicals are a group of synthetic, strongly paramagnetic compounds that have several characteristics that make them promising contrast enhancers.

Animals↗
PubMed1983

Work in progress: nuclear magnetic resonance study of a paramagnetic nitroxide contrast agent for enhancement of renal structures in experimental animals.

A piperidinyl nitroxide stable free radical derivative, TES, was tested as an NMR contrast enhancer of renal structures in normal animals and animals with experimentally induced unilateral renal ischemia, renal vascular congestion, and hydronephrosis. Physiologic measurements indicated that TES is rapidly excreted in the urine with a clearance rate equal to the glomerular filtration rate. Because the compound is strongly paramagnetic, it increases the observable NMR intensity within the kidneys and urine in relatively low doses (0.04 to 0.9 g/kg). TES-enhanced spin echo renal images clearly demonstrated the presence of disease and functional abnormalities in diseased kidneys. These abnormalities were either not evident or only indirectly suggested on nonenhanced NMR images.

Animals↗
PubMed1983

Neuroblastoma: diagnostic imaging and staging.

Results of computed tomography (CT), scintigraphy, excretory urography, and other imaging tests used to diagnose and stage 38 cases of neuroblastoma prior to treatment were reviewed. Findings of these examinations were correlated with clinical data, laboratory data, results of biopsy, and surgical findings. CT was the most sensitive single test (100%) for the detection and delineation of the primary tumor. Calcifications that suggested the histologic diagnosis of neuroblastoma were present in 79% of the cases. Rim calcifications, the most specific pattern for neuroblastoma, were identified in 29% of all cases. CT alone accurately staged 82% of cases; when complemented by bone marrow biopsy, staging accuracy was 97%. CT alone was more accurate than any combination of imaging tests that excluded CT. An algorithm using CT is presented for the diagnosis and staging of neuroblastoma at reduced cost and with increased efficiency.

Bone Marrow↗
PubMed1983

Recurrent neuroblastoma: the role of CT and alternative imaging tests.

One hundred twelve CT scans of 52 patients who were receiving treatment for neuroblastoma were reviewed for accuracy, and findings were correlated with data obtained from other imaging tests, physical examinations, laboratory tests, biopsies, surgery, and long-term clinical follow-up. CT was the most sensitive imaging test for tumor recurrence (85% detection rate), and it was also the most versatile in the ability to define recurrent disease in the retroperitoneum, liver, cranium, mediastinum, lymph nodes, and skeleton. All 30 tumor recurrences were detected by the combination of CT, bone-marrow biopsy, and selected spot radiographs at the sites of pain. CT was accurate and clinically useful both for assessing tumor response to therapy and for predicting findings at "second look" surgery (accuracy, 94%). CT is relatively cost effective by substituting for a more expensive but less accurate combination of competitive imaging studies.

Adrenal Gland Neoplasms↗
PubMed1983

Nuclear magnetic resonance contrast enhancement study of the gastrointestinal tract of rats and a human volunteer using nontoxic oral iron solutions.

Two dilute oral iron solutions, made from commonly available nonprescription dietary supplements, were found to enhance the gastrointestinal tract in nuclear magnetic resonance imaging of live rats and one human volunteer. The paramagnetic and pharmacologic properties of ferric ammonium citrate were more favorable than those of ferrous sulfate heptahydrate. The paramagnetic iron solutions shorten T1 and T2 relaxation times of water protons in the contrast media-filled gastrointestinal tract, producing easily observable change in NMR intensity. Because these iron solutions are available commercially and are known to be well tolerated, the clinical use of iron-containing NMR contrast agents for the gastrointestinal tract is feasible.

Animals↗
PubMed1983

Brain nuclear magnetic resonance imaging enhanced by a paramagnetic nitroxide contrast agent: preliminary report.

Contrast-enhancing agents for demonstrating abnormalities of the blood-brain barrier may extend the diagnostic utility of proton nuclear magnetic resonance (NMR) imaging. "TES," a nitroxide stable free radical derivative, was tested as a central nervous system contrast enhancer in dogs with experimentally induced unilateral cerebritis or radiation cerebral damage. After intravenous injection of TES, the normal brain showed no change in NMR appearance, but areas of disease demonstrated a dramatic increase (up to 45%) in spin-echo intensity and a decrease in T1 relaxation times. The areas of disease defined by TES enhancement were either not evident on the nonenhanced NMR images or were better defined after contrast administration. In-depth tests of toxicity, stability, and metabolism of this promising NMR contrast agent are now in progress.

Animals↗
PubMed1982

CT localization of occult secretory tumors in children.

Three seemingly occult secretory tumors in children (pheochromocytoma, ganglioneuroblastoma and islet cell carcinoma) were localized within the abdomen by computed tomography after other diagnostic imaging procedures had failed. The superb density resolution and tomographic formating of CT images make CT uniquely suited for the demonstration of small abdominal lesions. CT is recommended as a primary imaging modality for secretory tumors in children.

Adenoma, Islet Cell↗
PubMed1982

Reconstructive surgery for obstructing lesions of the intrathoracic trachea in infants and small children.

This is a report of ten infants and small children with congenital obstructive lesions of the distal trachea and main bronchi. Four were successfully resected. One with a distal segment stenosis required tracheal resection at age 6 wk, another with stenosis of the distal half of the trachea at age 18 mo, and 2 (1 with distal stenosis and 1 with tracheal hamartoma) at age 4 yr. All 4 are presently free of symptoms and their anastomoses have grown without stricture. A child with coil-spring mucosal stenosis of the left main bronchus developed an excellent airway following bronchoscopic removal of the folds, and a baby with tracheomalacia was successfully treated with a rib splint on a segment of distal tracheomalacia, but she died later of associated cyanotic congenital heart disease. Four babies died with airway obstruction in the newborn period. Two with critical distal stenoses died before tracheal reconstruction could be performed. Two died following emergency resections in which all of the congenital stenosis could not be removed. In both, stenotic trachea remained despite operation. All of these infants had complete cartilage rings the entire length of the trachea. Congenital lesions of the distal trachea may become suddenly life-threatening at birth or during the onset of a respiratory infection. An abrupt or insidious onset of airway symptoms requires an expeditious diagnostic evaluation to define the tracheobronchial anatomy, and the operating team has to be prepared for emergency tracheal reconstruction.

Abnormalities, Multiple↗
PubMed1982

Direct magnification radiography of the newborn infant.

Recent advances in technology have made direct radiographic magnification of the newborn infant clinically feasible. A microfocus radiographic tube and a rare-earth, high-speed recording system were combined to obtain more than 2,000 radiographs at magnifications of 2-2.5. Special positioning devices permitted imaging of even those infants confined to incubators and connected to life-supporting systems. When quantitatively compared with three conventional contact radiographic systems with respect to resolution, contrast, and noise, magnification radiography showed overall superiority of image characteristics. Definition of subtle abnormalities and anatomically small structures permitted diagnoses which could not be made from conventional images. Furthermore, infant radiation exposure was markedly less (15 mR [3.9 mC/kg] maximum skin exposure) as compared with conventional contact radiographic systems (24 mR [6.1 mC/kg] to 45 mR [11.6 mC/kg]).

Humans↗
PubMed1982

Computed tomographic scanning in children: II. An updated comparison of radiation dose and resolving power of commercial scanners.

Surface and internal radiation doses for abdominal CT of children were determined using child-sized phantoms and seven commercial models of CT body scanners. High contrast resolving power and low contrast discrimination for each scanner were determined simultaneously with radiation dose measurements and the results were compared with those from a similar study conducted in 1977 with earlier CT models. The average circumferential surface doses for simulated pediatric CT body examinations were 31% lower in this study compared to 1977 results, with a mean of 1.5 rad (0.015 Gy) vs. 2.2 rad (0.022 Gy) respectively. At the same time, resolving power for high (12%) contrast improved by 31% to a mean of 1.38 mm from 2.00 mm. All scanners in the present study could resolve low contrast differences of 1/4% for a 5 mm object.

Child↗