Biomedical subjects

C B Higgins

Publications and source records attributed to C B Higgins.

At least 613 records · Page 34Linked to original sources

PubMedDate not supplied

Relative intensity of abdominal organs in MR images.

Knowledge of the normal relative intensity of organs and tissues is a valuable aid to clinical interpretation of magnetic resonance images. In this study the in vivo spin echo image intensities of normal parenchymal organs and other structures in the upper abdomen were evaluated for eight parameter combinations. The examinations of 40 patients were used. Image intensity and calculated T1, T2, and spin density values were obtained for liver, spleen, pancreas, renal cortex, renal medulla, bone marrow, skeletal muscle, and fat. Repetition times (TR) of 500, 1,000, 1,500, and 2,000 ms and echo times of 28 and 56 ms were used. The T1 and T2 values and relative spin density were calculated using a new algorithm. Liver had the smallest relative standard deviation of T1 of all the tissues studied. For comparison purposes, relative image intensities were calculated by normalizing them to the intensity of liver in the same image. The resulting compiled data show the normal ranks and ranges for relative intensity for the tissues in each of eight types of spin echo images. Although images with short TR and echo time (TE) are known to display the greatest T1 contrast, the mean relative intensities of all tissues except muscle and fat in the TR = 500 and TE = 28 ms images were within 20% of liver. A much larger spread in the normal relative intensities was observed with longer TE and TR.

Abdomen↗

PubMedDate not supplied

MR image contrast and relaxation times of solid tumors in the chest, abdomen, and pelvis.

A retrospective study of 121 patients with tumors in the chest, abdomen, and pelvis was made to assess the degree of contrast between solid tumors and adjacent tissue on magnetic resonance (MR) spin echo (SE) images. Tumors examined were hepatomas (five patients), liver metastases (17), hemangiomas (seven), biliary carcinomas (eight), pancreatic carcinomas (five), renal tumors (15), adrenal tumors (eight), uterine tumors (17), bladder carcinomas (five), prostatic carcinomas (13), bone tumors (six), and lung carcinomas (15). A long repetition time (TR) and a long echo time (TE) were found the most useful to delineate tumors from liver, renal tumors from kidney, lung carcinoma from lung, pelvic tumors from muscle, and uterine tumors from the myometrium. A short TR and short TE provided the best contrast between tumors and fat and bone marrow. Therefore, for detection and staging of tumors, both a sequence with short TR and short TE and one with long TR and long TE are necessary. Pancreatic carcinomas were difficult to differentiate from liver and pancreas on all SE sequences used in the study. Contrast of adrenal tumors was independent of the sequence used. Some adrenal tumors were hypointense and some similar in intensity to the kidney. Further MR characterization of the tumors was limited.

Abdominal Neoplasms↗

PubMedDate not supplied

MR imaging of intramuscular hemorrhage.

This retrospective study was performed to (a) analyze the appearance of normal striated muscle using the spin echo (SE) technique and (b) evaluate the potential of magnetic resonance (MR) imaging for demonstrating intramuscular bleeding. Magnetic resonance examinations of 30 patients imaged for reasons other than muscular disorders were reviewed. Normal striated muscle was always imaged with a lower intensity than fat because muscle had a longer T1 and a shorter T2 than fat. Furthermore, the spin density of muscle was less than that of fat. The best contrast between the two tissues was obtained with a short repetition time (TR) of 0.5 s and a long echo time (TE) of 56 ms. In addition, five MR examinations from three patients with intramuscular bleeding were assessed. In one case the CT examination was also available for comparison. In every case MR permitted the diagnosis and demonstrated the precise extent of intramuscular bleeding and its regression after therapy. The MR diagnosis of intramuscular bleeding was readily performed because of the excellent contrast resolution of the technique. These lesions were always brighter than the surrounding normal muscle. The optimum SE technique, which enhanced contrast between the muscle and the site of bleeding, was a long TR of 2.0 s and a long TE of 56 ms. The T1 and T2 relaxation times of intramuscular bleeding were always longer than those of normal striated muscle. Preliminary results indicate that MR is very sensitive for the demonstration of intramuscular bleeding.

Adolescent↗

PubMedDate not supplied

MR imaging of an intrapericardial pheochromocytoma.

The magnetic resonance (MR) appearance of an intrapericardial pheochromocytoma is reported, and the role of MR, compared with CT and a 131I-metaiodobenzylguanidine scan in delineating masses from cardiac and vascular structures in the mediastinum is discussed.

3-Iodobenzylguanidine↗

PubMedDate not supplied

Cine-computed tomography of arrhythmogenic right ventricular dysplasia.

The CT diagnostic features of arrhythmogenic right ventricular dysplasia (Uhl anomaly) are described in a 72-year-old man. High speed cine-CT was performed using millisecond exposures and multilevel scanning. Ventricular morphology and function were evaluated, and findings were compared with two-dimensional echocardiography and equilibrium gated blood pool imaging. Cine-CT showed a dilated hypokinetic right ventricle with a markedly thin anterior wall and normal left sided chambers. The clinical aspects of Uhl anomaly are reviewed.

Aged↗

PubMedDate not supplied

Cine-computed tomography of Ebstein anomaly.

A case of Ebstein anomaly is reported, and the diagnostic potential of cine-CT in assessing the magnitude of the anatomic changes and the presence of right to left intracardiac shunting is evaluated.

Cineradiography↗

PubMedDate not supplied

MR imaging of pathologic abdominal fluid collections.

A retrospective comparison was made of the capability of magnetic resonance (MR) imaging and CT to display and characterize pathologic abdominal fluid collections. Fluid collections in 41 patients were analyzed: ascites (seven patients), hematoma (five), pancreatic pseudocyst (four), biloma (two), abscess (four), simple renal cyst (nine), hemorrhagic renal cyst (two), hydronephrosis (four), hemonephrosis (two), and cystic metastases (two). Most fluid collections were equally demonstrated by the two modalities. Walls around fluid collections were better demonstrated CT. Six fluid collections appeared heterogeneous on MR but were homogeneous or nearly so on CT.

Abdomen↗

PubMedDate not supplied

MR imaging of body fluid collections.

To evaluate the potential of magnetic resonance (MR) to characterize body fluids in vivo, we determined the relaxation times and the relative MR signal intensities of 42 body fluid collections in 42 patients. Twelve normal volunteers served as controls. We also studied albumin solutions at different concentrations and blood at various periods in vitro. Because of their long T1 relaxation times, most nonhemorrhagic fluid collections had low to intermediate intensity on images obtained with short repetition time (TR) and short echo time (TE) settings. Although the relaxation times and relative MR signal intensities of noninfected collections differed from those of infected collections, the values overlapped. On images obtained with short TR and short TE, blood in acute hemorrhages had intermediate signal intensity and serum in subacute hemorrhagic collections was the only pathologic fluid producing high signal intensity. Because of their relatively long T2 values, all the fluid collections were intense on images obtained with long TR and long TE settings; consequently, differences in intensity were less evident than on images obtained with short TR and short TE settings. Magnetic resonance allows reliable discrimination of subacute hemorrhagic collections from collections of other types, but the differentiation between acute hemorrhagic collections; nonhemorrhagic, noninfected collections; and nonhemorrhagic, infected collections is less accurate.

Adolescent↗

PubMedDate not supplied

MR imaging of diffusely infiltrating gastric carcinoma.

Magnetic resonance imaging of a diffusely infiltrating gastric carcinoma showed a markedly thickened gastric wall with low signal intensity on T1 and T2 weighted images. The T2 relaxation of the thickened gastric wall was very short, which was consistent with the histologically proven fibrous nature of the lesion.

Adenocarcinoma↗

PubMedDate not supplied

MR imaging of the thoracic aorta in Marfan patients.

A characteristic shape of the ascending aorta has been reported in patients with Marfan syndrome. To evaluate the capability of magnetic resonance (MR) imaging to distinguish between marfanoid and other aortic aneurysms, 11 Marfan patients (group 1), eight patients with ascending aorta enlargement (group 2), and 20 normal subjects (group 3) had transverse and sagittal MR of the thoracic aorta. Aortic diameter was measured at the sinuses of Valsalva (SV), the caudal portion of the ascending aorta, the prearch region (PA), the middle arch, and the descending aorta. The ratio SV/PA was significantly greater (p less than 0.001) in group 1 compared with groups 2 and 3. The SV/PA in all Marfan patients exceeded 1.4 but was less than 1.3 in subjects of groups 2 and 3. Magnetic resonance imaging provides definitive measurements of aortic dimensions and is potentially the method of choice for establishing the diagnosis of aortic involvement in Marfan syndrome and monitoring the course of aortic enlargement.

Aorta↗

PubMedDate not supplied

MR imaging of complications of aortic surgery.

Sixteen patients with a variety of complications of aortic surgery were evaluated with magnetic resonance (MR) imaging. More than one complication occurred in seven patients, resulting in the following types of abnormalities: graft occlusions, two; graft infections; five; pseudoaneurysms or aneurysmal dilatation of graft anastomoses, 10; perigraft hemorrhages, four; and aortoenteric fistulas, two. The MR findings were verified by surgery in 10, by CT in four, and by angiography in 11 patients. The size and extent of pseudoaneurysm or anastomotic dilatation, the presence of thrombus and vessel occlusion, the extent of abscesses, and the effect of pseudoaneurysms and abscesses on adjacent structures were readily demonstrated by MR. The size of the residual lumen in the case of thrombosis could be assessed. Abscesses were identified by their characteristic signal increase with long repetition rates and long echo delays. Magnetic resonance was also able to exclude suspected complications such as perigraft infection, hemorrhage, and graft occlusion in four patients.

Abscess↗

PubMedDate not supplied

Quantitation of intracardiac shunts by cine-CT.

Quantitation of intracardiac shunts is important in the evaluation of congenital heart disease and ventricular septal defects postmyocardial infarction. Shunt detection and quantitation is currently performed by either oximetry or radionuclide angiography. Oximetry is an invasive technique and radionuclide angiography, although noninvasive, does not have sufficient spatial resolution to provide detailed anatomic information. The present study evaluated a new technique for quantitating right-to-left shunts by analysis of indicator dilution curves acquired noninvasively using cine-CT. This technique was evaluated in a phantom and in postoperative dogs with a surgically created variable shunt. The phantom model demonstrated the accuracy and reproducibility of the curve analysis algorithm, and the canine model permitted the comparison of oximetry with cine-CT for shunt quantitation. Cine-CT accurately estimated right-to-left shunt fraction when compared with oximetry (r = 0.91) and is more sensitive than oximetry in detecting small shunts. The results of this study suggest that contrast enhanced cine-CT provides a precise noninvasive technique for measuring shunt lesions in congenital and acquired heart diseases.

Animals↗

PubMedDate not supplied

MR imaging of low signal intensity pulmonary lesions using flow-sensitive techniques.

Various spin echo techniques can be used to define the nature of low signal intensity lesions of the lung. A pulmonary arteriovenous malformation and a chronic pulmonary hematoma had a similar appearance on standard spin echo magnetic resonance (MR) images. Both lesions demonstrated central absence of signal surrounded by a thin rim of tissue, suggesting a vascular lesion. For further characterization of these lesions, a rotating gated MR technique was used in which images are obtained at different points in the cardiac cycle, such that pulsatile flow alters signal intensity with velocity changes during the cardiac cycle. Phase images also discriminated flowing blood in the arteriovenous malformation from stationary lung tissues, whereas the hematoma was not distinguished from lung parenchyma. Rotating gated sequences and reconstructed phase images may be useful in determining the etiology of low signal intensity pulmonary lesions.

Adult↗

PubMedDate not supplied

High signal intensity lesions of the chest in MR imaging.

The majority of pathologic lesions in the lung and mediastinum have relatively long T1 and T2 relaxation times and consequently yield medium to low signal intensity on T1-weighted images. Pulmonary lesions with high signal intensity on T1-weighted images are unusual and raise a special group of diagnostic considerations. In the current study, a mass with a lesion/fat signal intensity ratio of greater than 0.7 on a T1-weighted sequence was considered high signal intensity. The nature of these masses was ganglioneuroma or ganglioneuroblastoma (n = 3), atrial lipoma (lipomatous atrophy of the interatrial septum) (n = 3), pheochromocytoma (n = 2), bronchogenic cyst (n = 2), lymphangioma (n = 1), teratoma (n = 1), and a variety of primary and metastatic tumors of the mediastinum and lung. A single pathologic structure of these lesions was not present, but rather several underlying tissue compositions were noted, including fat, subacute hemorrhage, myxoid material, and cellular composition with high cytoplasmic/nuclear ratio. Thus, high signal intensity lesions of the thorax on T1-weighted images should suggest a number of differential diagnoses.

Female↗

PubMedDate not supplied

MR imaging of unilateral pulmonary artery anomalies.

Magnetic resonance (MR) imaging of the pulmonary arteries was performed in seven children with unilateral pulmonary artery abnormalities. Five had congenital absence or interruption of a pulmonary artery; two had postsurgical occlusion or narrowing of a pulmonary artery. A small patent hilar pulmonary artery was identified in one of the five cases of congenital pulmonary artery interruption or absence. Occluding thrombus was identified in the right pulmonary artery of one child following pulmonary artery banding. In another case marked narrowing of the right pulmonary artery was identified secondary to migration of a pulmonary artery band. The MR findings were confirmed by angiography in all cases. Magnetic resonance appears to be a useful noninvasive modality for accurate anatomic depiction of unilateral pulmonary artery abnormalities in childhood. It may be especially valuable for diagnosis of pulmonary artery stenosis or occlusion following surgical treatment of congenital heart disease.

Adolescent↗

PubMedDate not supplied

MR imaging of double outlet right ventricle.

Five patients with angiographically proven diagnosis of double outlet right ventricle (DORV) were studied with magnetic resonance (MR) imaging. Magnetic resonance was compared with angiography and echocardiography. Contiguous electrocardiographic-gated spin-echo images were acquired on a 0.35 T imager. Magnetic resonance was equivalent to echocardiography in demonstrating relative relationships of the great arteries with respect to each other, the relative positions of the great arteries with respect to the ventricular septal defect (VSD), and the caliber of the great vessels. It was comparable in visualization of the size and position of the VSD and position of the atrioventricular valves. Due to limited spatial resolution, MR failed to identify chordal straddle of a tricuspid valve and incorrectly interpreted pulmonary stenosis as pulmonary atresia. A small patch leak of an internal baffle was only visualized on angiography. We conclude that MR is superior to echocardiography in the noninvasive assessment of the spatial arrangement and caliber of the great vessels. As such, it is a useful adjunct to echocardiography in the noninvasive assessment of DORV.

Adult↗

PubMedDate not supplied

Detection of aortic arch thrombus using MR imaging.

Three patients with peripheral embolization and negative echocardiographic examinations were studied with MR imaging. Magnetic resonance imaging detected aortic arch thrombi in the absence of aortic aneurysm, dissection, or ulcerated plaques. By combining spin echo and cine MR sequences, MR enabled us to characterize and contrast intravascular mural thrombi reliably without application of contrast media. Thus we are assisted in the identification of patients at risk for embolization from an often overlooked source: the thoracic aorta.

Aged↗

PubMedDate not supplied

MR measurement of blood flow in the true and false channel in chronic aortic dissection.

Velocity encoded (VEC) cine MR imaging is a new noninvasive technique for the quantification of blood flow velocity in the cardiovascular system. Six patients with type B aortic dissection underwent VEC cine MR imaging at 1.5 T. This technique provides cine MR magnitude and VEC phase images at approximately 16 equally spaced intervals during an average cardiac cycle. A region of interest encompassing a vascular structure, i.e., false channel, provides a spatially averaged velocity for the time interval at which the image was acquired. Interpretation of velocity values from the 16 intervals during the cardiac cycle provides a temporally average velocity. Velocity mapping across the aortic lumen in these six cases showed average spatial and temporal velocity of 13.4 +/- 1.49 cm/s in the true channel and 3.1 +/- 0.84 cm/s in the false channel (p less than 0.05). The peak systolic velocity (temporal peak) was 43.6 +/- 7.20 cm/s in the true channel and 14.3 +/- 2.30 cm/s in the false channel (p less than 0.05). The flow volume per cardiac cycle was not significantly different between the ture (23.1 +/- 5.04 ml/cycle) and false channel (27.1 +/- 10.14 ml/cycle). There was substantial retrograde flow in the false channel of two patients. The intraobserver and interobserver variability was less than 10% (r = 0.98 to 0.99) for the measurement of flow parameters in both the true and the false channel. We conclude that VEC cine MR imaging demonstrates substantial differences in the hemodynamic pattern in the true and false channel in aortic dissection.

Adult↗