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Biomedical subjects

C B Higgins

Publications and source records attributed to C B Higgins.

At least 343 records · Page 19Linked to original sources
PubMed1985

Assessment of severity of experimental pulmonary edema with magnetic resonance imaging. Effect of relaxation enhancement by Gd-DTPA.

This study was done to demonstrate the capability of magnetic resonance imaging (MRI), using a spin-echo technique to detect permeability pulmonary edema in vivo, to correlate the signal intensity to the water content of the lung, and to assess the influence of administration of gadolinium-DTPA upon this relationship. Pulmonary edema was induced in 28 rats by intravenous injection of oleic acid (0.05-0.1 cc/kg). This was detected in all animals on images obtained with a repetition time (TR) of 2.0 seconds and echo times (TE) of 28 or 56 msec as increased signal intensity. Compared with control animals, the intensity was increased primarily in the dependent and peripheral portions of the lung. There was a significant linear relationship between the mean signal intensity, obtained from the area of both lungs within one slice, and the water content of both lungs (r = .94). Intravenous administration of gadolinium (Gd)-DTPA, 5 minutes prior to imaging, produced an easily observable increase in signal intensity on images of short TR (0.5 second) in the edematous lung tissue. However, these values did not exceed the intensities obtained without Gd-DTPA, if a long TR (2.0 seconds) was used for imaging. Thus, MRI has the capability for quantitating the severity of oleic acid-induced pulmonary edema. Gd-DTPA distributes rapidly into permeability pulmonary edema. It allows improved sensitivity at shorter pulse sequence repetition times and thus may diminish imaging time.

Animals↗
PubMed1985

Effects of intravenous administration of a new nonionic dimeric contrast medium on the coronary circulation. Comparison with monomeric ionic and nonionic media.

Contrast media injected into the circulation produce a variety of cardiovascular effects. Agents with low osmolality and low concentrations of cations cause considerably less hemodynamic effects. This study compared the effects of a nonionic dimer, iotrol, which has an osmolality (340 mosm/kg) close to that of serum (290 mosm/kg), with a standard ionic monomer, meglumine diatrizoate, and a nonionic monomer, iosimide. The effects of intravenous bolus injection of these three contrast agents on coronary and systemic hemodynamics were studied in eight anesthetized dogs. The influence of the contrast media on subendocardial and subepicardial perfusion was assessed by injecting radioactive microspheres into the left atrium 30 seconds after injection of the media. Alterations in coronary hemodynamics occurred with both iosimide and meglumine diatrizoate. Iotrol produced minimal changes in coronary hemodynamics. Thus, iotrol is the least perturbing contrast indicator and seems the best for use in quantitative digital subtraction and dynamic computed tomography studies designed to measure myocardial perfusion.

Animals↗
PubMed1985

Infected aortoiliofemoral grafts: magnetic resonance imaging.

Three patients with proved infected aortoiliofemoral grafts were examined by magnetic resonance (MR) imaging using a spin echo technique. MR clearly identified the perigraft abscess, the involvement of adjacent structures, and the longitudinal extent of the process in all patients. The MR findings were: Abscesses create a high signal intensity, somewhat less than fat. The perigraft abscess has a great contrast with the signal void of flowing blood in the graft. Inflammatory changes cause an inhomogeneous intermediate signal, slightly more intense than muscle. Both abscesses and edematous areas increase their signal intensity with long repetition rates and long echo delays. Areas of gas appear black. They cannot be distinguished from calcified plaques. Additional information is gained about the graft patency. Although the specificity has to be proved, MR imaging is sensitive in the detection of infected grafts and for defining the longitudinal extent of the perigraft abscess.

Aged↗
PubMed1985

Comparison of magnetic resonance imaging and ultrasonography in the evaluation of abdominal aortic aneurysms.

Magnetic resonance imaging (MRI) was used to evaluate abdominal aortic aneurysms in 27 patients. The findings were compared retrospectively with CT, ultrasound (US), and angiography in 17 cases and prospectively with US in 10 cases. MRI identified the renal arteries in all cases, demonstrated involvement at or above the origin of the renal arteries in eight patients, and showed extension of the aneurysm into the iliac arteries in 12 cases. The outer dimension of the aneurysm, the diameter of the residual lumen, and the length of the aneurysm were measured easily from the MR images. The measurements of transverse dimension of the abdominal aortic aneurysm were similar for MRI, CT, and US. MRI more accurately defined extension above the renal arteries and below the aortic bifurcation. It is concluded that MRI provides the necessary information for the surveillance and preoperative evaluation of abdominal aortic aneurysms.

Aged↗
PubMed1985

Obstetrical magnetic resonance imaging: maternal anatomy.

Eleven patients whose pregnancies were at 34-36 weeks of gestational development underwent magnetic resonance (MR) imaging. Images of the maternal pelvis were assessed for anatomical changes of pregnancy in comparison with MR images of five non-pregnant volunteers. The relationship of the fetal presenting part to the internal os of the cervix was seen in all patients. Effacement of the cervix was identified when present. The maternal spine demonstrated disk abnormalities in nine patients. Changes in venous flow patterns were readily identified in all patients. The inferior vena cava was flattened or obliterated, a high signal was present in the iliac vessels (TE 56), and large collateral vessels were present.

Adult↗
PubMed1985

Obstetrical magnetic resonance imaging: fetal anatomy.

Nine patients who were 34-36 weeks pregnant underwent magnetic resonance (MR) imaging. Sagittal images using spin echo technique (TR 2.0 sec, TE 28 msec) were optimal for delineating fetal anatomy. The fetal cardiovascular, pulmonary, and central nervous systems were depicted in all cases. The heart and major vessels were readily seen due to the natural contrast of flowing blood. The intensity of the fluid-filled lungs greatly increased with a longer TR or TE, delimiting thorax from liver. The brain was relatively featureless due to the lack of gray-white matter differentiation. The umbilical cord within the amniotic fluid and its insertion into the placenta and fetus was identified in all cases. MR is a new modality for fetal imaging that offers tissue-characterization information that complements the superior anatomic detail of ultrasound scanning.

Amniotic Fluid↗
PubMed1985

Magnetic resonance imaging of prosthetic heart valves.

To evaluate the safety of magnetic resonance (MR) imaging of prosthetic heart valves, nine different synthetic and tissue valves were studied ex vivo. Deflection was measured in 0.35-tesla (T) and 1.5-T superconducting magnets and at the edge of the bore of a 2.35-T electromagnet in field gradients of 5, 1.1, and 6.3 mT/cm, respectively. No valve deflected in the 0.35-T magnet; six synthetic valves deflected 0.25 degrees-3 degrees in the 1.5-T magnet; all valves deflected 1 degree-27 degrees at the edge of the 2.35-T magnet. Each valve was then submerged in a vial of water and the temperature was measured immediately before and after each of two spin-echo imaging sequences in the two superconducting magnets. No significant temperature rise followed exposure in either magnet. Image distortion varied from negligible to severe in both imagers; magnitude of distortion paralleled magnitude of deflection. These data suggest that patients with present-day prosthetic heart valves can be safely imaged in present-day MR imagers and that prosthesis-induced artifacts will not interfere with interpretation in most instances.

Bioprosthesis↗
PubMed1985

Aortic dissection: magnetic resonance imaging.

Fifteen patients with suspected or known aortic dissection were imaged with magnetic resonance (MR). Thirteen of these patients were eventually shown to have dissection. In most instances the diagnosis was established by aortography and/or computed tomography (CT) prior to the MR study. Surgical proof (6/13) and/or aortographic proof (10/13) were available in 11/13 patients with aortic dissection. MR demonstrated the intimal flap and determined whether the dissection was type A or type B. In addition, MR: differentiated between the true and false lumens; determined the origins of the celiac, superior mesenteric, and renal arteries from the true or false lumen in the cases where the dissection extended into the abdominal aorta (8/12); allowed post-surgical surveillance of the dissection; and identified aortoannular ectasia in the three patients who had Marfan syndrome. In addition to the 13 cases with dissection, there were two cases in whom the diagnosis of dissection was excluded by MR. Our early experience suggests that MR can serve as the initial imaging test in clinically suspected cases of aortic dissection and that the information provided by MR is sufficient to manage many cases. Additionally, MR obviates the use of iodinated contrast media.

Adult↗
PubMed1985

Magnetic resonance imaging of the heart: a review of the experience in 172 subjects.

Gated magnetic resonance (MR) imaging was used to evaluate central cardiovascular anatomy in 172 subjects, 31 of whom were healthy volunteers. Using the spin-echo technique, images of diagnostic quality were obtained in 93% of cases with TE = 28 msec and in 65% of cases with TE = 56 msec. Transverse multisection sequences encompassing most of the left ventricle required approximately 6-8 minutes. Corroborative studies were available in 134 of 141 patients who had cardiovascular disease; two dimensional echocardiograms and angiography in 133 and 100 patients, respectively. Gated MR demonstrated the wall thinning and complications caused by prior myocardial infarctions and high signal intensity of the myocardium at the site of acute myocardial infarctions. MR accurately demonstrated anatomic abnormalities owing to hypertrophic and congestive cardiomyopathies, congenital abnormalities of the heart and great vessels, rheumatic heart disease, pulmonary hypertension, and cardiac and paracardiac masses. Depiction of cardiovascular anatomy and pathoanatomy was attained without the use of any contrast media. Consequently, gated MR is an effective technique for cardiac diagnosis. The short time required for tomographic examination of the entire heart using the multisection technique renders this a practical cardiac imaging modality.

Adolescent↗
PubMed1985

ECG-synchronized cardiac MR imaging: method and evaluation.

An electrocardiographic (ECG) sensing and gating device compatible with a 0.35-tesla (T) magnetic resonance (MR) imager has been developed and used to produce 802 MR images of the heart in 30 patients. The instrument consists of an isolated acquisition module, an electrically floating preamplifier, and a monitor gating module. Two spin-echo images were acquired for each of five, 0.7-cm thick, transaxial sections from the base to the apex of the heart during each ECG-synchronized imaging run. Image quality was assessed in a blind study by two investigators, on a scale from 0 to 3, as diagnostic [2-3] or nondiagnostic [0-1]. There was agreement in 91.4% of their assessments of diagnostic images (68.1% of the images studied). Resolution of heart anatomy on the MR images was adversely affected by prolonged spin-echo time delay, imaging in late diastole, image acquisition at the cardiac apex, irregular triggering, and artifacts. The synchronization of gradient pulses to the ECG at 0.35 T appears safe for patients, permits diagnostic resolution of images, allows image acquisition at distinct points during the cardiac cycle, and enables monitoring of patients during imaging.

Adult↗
PubMed1985

Characterization of lymphadenopathy by magnetic resonance relaxation times: preliminary results.

The purpose of this study was to evaluate the ability of magnetic resonance (MR) to enable characterization of disease within lymph nodes and differentiation between benign and malignant lymph nodes. Ninety-three patients were examined. Normal and malignant lymph nodes were excised from seven patients, and the T1 and T2 relaxation times were analyzed in vitro using spectroscopy. In 86 patients, T1 and T2 relaxation times of the lymph nodes were determined from MR images. Spectroscopic analysis revealed an increase in the T1 and T2 values of nodes involved by neoplasm compared with uninvolved nodes in an individual case. Comparison of measurements from 28 lymph nodes analyzed in vitro using spectroscopy showed an overlap of the T1 and T2 values between normal and malignant lymph nodes. T2 relaxation times and relative spin density values were greater for acute inflammatory nodes than for nodes involved by granulomatous diseases (tuberculosis and sarcoidosis) or nodes replaced by lymphoma or metastasis. Changes in T1 relaxation values were not specific. The measurements of T1 and T2 relaxation times and relative spin density showed an overlap between nonspecific lymphadenopathy, nodes involved by granulomatous diseases, and malignant nodes. Differentiation between these various nonacute types of enlarged lymph nodes could not be achieved using current MR parameters.

Adolescent↗
PubMed1985

Gated MR imaging of the heart: intracardiac signals in patients and healthy subjects.

The appearance of intraluminal signal in the cardiac chambers, the descending aorta, and blood vessels was studied in healthy subjects and patients with myocardial disease on first and second spin-echo gated magnetic resonance images. Signal was present in the cardiac chambers and the aorta at various phases of the cardiac cycle when physiological or pathological slow flow conditions are expected in healthy subjects and in patients. Healthy individuals tended to show signal in the ventricles and aorta during end-diastole, and signal was less likely to be present at higher heart rates and in systolic images. In patients with regional or global left ventricular dysfunction, intraventricular signal tended to persist into systole. Surprisingly, intraventricular signal was not present with increased frequency adjacent to infarcted regions of the myocardial wall. Thus, the mere presence of intracavitary signal cannot be used as an indicator of either regional or global cardiac contraction abnormalities. In the left atrium, signal was often present during systole. Physical factors determining the appearance of signal of flowing blood are discussed in an Appendix.

Adult↗
PubMed1985

Abdominal venous system: assessment using MR.

Twenty-five patients with known or suspected evidence of venous disease based on results of computed tomography, angiography, or ultrasound were imaged with magnetic resonance (MR) to determine the MR characterization of venous abnormalities. MR findings were proved by laparotomy or autopsy in 18 of 25 cases. In seven of 25 patients in whom only biopsy was performed, the MR findings were correlated with findings from other radiologic tests. On MR, the inferior vena cava (IVC), portal vein, and their major tributaries were seen in all but two cases. In those two, identification of collaterals led to the correct diagnosis of splenic vein thrombosis in one case and left renal vein thrombosis in another. MR imaging helped identify intraluminal thrombi in the IVC (12 of 12 cases), portal vein (two of two cases), renal veins (seven of seven cases), superior mesenteric vein (one case), and iliac veins (seven of seven cases). Intraluminal signal intensity secondary to slow blood flow seen in five patients was always differentiated from the thrombus. MR imaging helped identify correctly the nature of the thrombus in 11 of 16 patients. In five patients, the differentiation between tumor thrombus and blood clot thrombus was not possible. Involvement of the IVC wall by tumor was seen in four cases. MR imaging also accurately depicted slow flow in obstructed or constricted veins; encasement, compression, or displacement of veins without intraluminal occlusions; and the presence of venous collaterals. The MR imaging evaluation of venous abnormalities is accurate, easily performed, and will probably become an important application.

Abdomen↗
PubMed1985

Peripheral vascular disease: correlation of MR imaging and angiography.

The capability of magnetic resonance (MR) imaging for detecting aortic, iliac, and femoral stenoses and occlusions was evaluated. Multisection spin-echo studies at 0.35 tesla were obtained of the infrarenal aorta to the femoral bifurcation in 24 patients, all of whom had undergone intraarterial angiography within 14 days of imaging. Transaxial MR images were compared with the angiograms. Arterial stenoses and occlusions in these vessels detected by MR imaging correlated with angiographic findings in 91% of the instances. Protrusional atherosclerotic plaques and occlusions and stenoses in the aortoiliac region were demonstrated accurately on MR images; complications of previous vascular surgery, such as aneurysms at sites of previous anastomoses or endarterectomy, were also identified. Due to the limited spatial resolution, MR images failed to demonstrate some femoral stenoses. MR imaging may be used for evaluation of aortoiliac vascular disease and for follow-up study after surgical revascularization. However, the limited spatial resolution, noncomposite display of the aortoiliofemoral circulation, and lack of evaluation of peripheral runoff provided by current MR imaging techniques militate against its replacing angiography prior to vascular intervention.

Angiography↗
PubMed1985

MR imaging using specialized coils.

The purpose of this study was to evaluate the clinical utility of specialized coils with magnetic resonance (MR) imaging and to determine the potential improvement in the signal-to-noise ratio (SNR) provided by the various coils. A total of 48 patients were studied-33 with surface coils and 15 with limb coils. MR imaging was performed with a superconducting magnet operating at 0.35 T. Two applications of surface coils were evaluated; one used for both transmitting and receiving and the other used only for receiving. Structures studied with the surface coils included the orbit, carotid artery, cervical and lumbar spine, parotid and thyroid glands, other neck structures, femoral artery, kidney, prostate, hip, and heart. The regions studied with the limb coil were the ankle, knee, wrist, elbow and popliteal artery. We calculated the SNR, and the results demonstrated a marked improvement with the specialized coils: a twofold increase for the 10-cm surface coil versus the head coil and a 4.6-fold increase compared with the body coil, a 2.3-fold increase for the 20-cm surface coil compared with the body coil, and 2.8- and 6.4-fold increases for the limb coil versus the head coil and the body coil, respectively. The use of specialized coils was feasible in the clinical setting and they provided a marked improvement in the image SNR, which facilitated the imaging of small and superficial structures.

Adolescent↗
PubMed1985

Lipomatous tumors and tumors with fatty component: MR imaging potential and comparison of MR and CT results.

This retrospective study was performed to assess the potential of magnetic resonance (MR) imaging for demonstrating various types of lipomatous tumors and tumors with fatty component and to compare the results of MR with those of computed tomography (CT). MR examinations of 17 patients with 18 lipomatous tumors (16, benign; two, liposarcoma) and two patients with fibrosarcomas were reviewed; CT scans were available for comparison in all patients. In the 16 benign lesions (12 benign lipomas, two ovarian dermoid cysts, and two renal angiomyolipomas), the fatty component of the tumors was readily demonstrated by both MR and CT. The T1 and T2 relaxation times and spin density of benign lipomatous tumors were in a range similar to those of normal subcutaneous fat. Differentiation between lipomas and liposarcomas was achieved with both MR and CT. On MR images using a short repetition time (TR = .5 sec), liposarcomas (long T1) were imaged with a lower MR intensity than lipomas (short T1).

Adolescent↗
PubMed1985

Blood flow imaging with MR: spin-phase phenomena.

Blood flow phenomena occurring when flow is within the magnetic resonance (MR) imaging plane were analyzed. In this situation, the signal intensity of vascular lumina is predominantly determined by spin-phase change phenomena, and section transition effects of moving spins can be neglected. In this paper, we develop the concepts of in-plane flow, with emphasis on the notion that the spatial variations in velocity and acceleration of blood, which mainly occur along vessel walls, are important determinants of intravascular signal loss in MR images. Flow patterns in the large mediastinal arteries were qualitatively and quantitatively analyzed in six healthy subjects and 14 patients with hemodynamic abnormalities using multiple electrocardiograph-gated image acquisition; ungated studies of 30 patients were analyzed for venous flow effects. Intraluminal signal was strongly dependent on the phase of the cardiac cycle and the echo number. Signal loss was found to occur along vessel walls, in vascular bends, and at bifurcations.

Abdomen↗