Biomedical subjects
M R Fisher
Publications and source records attributed to M R Fisher.
Musculoskeletal case of the day.
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MR imaging of myocardial sarcoidosis.
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Endometrial carcinoma staging by MR imaging.
The potential of magnetic resonance (MR) imaging in the detection of endometrial carcinoma and in the assessment of its extent was evaluated prospectively in 51 patients clinically suspected of having the disease. MR imaging findings were compared with the results of surgical-pathologic staging and lymph node sampling following hysterectomy. Histologic findings showed 45 patients to have endometrial carcinoma, three to have no residual tumor after dilatation and curettage, and three to have adenomatous hyperplasia of the endometrium. MR imaging demonstrated an endometrial abnormality in 43 of the 51 patients (84%). Endometrial carcinoma could not be differentiated from adenomatous hyperplasia or blood clots. Therefore, MR imaging was not specific for tumor detection, and histologic diagnosis remains essential. The overall accuracy of MR imaging in staging endometrial carcinoma was 92%; its overall accuracy in demonstrating the depth of myometrial invasion was 82%. Demonstration of lymphadenopathy and adnexal or peritoneal metastases by MR imaging was suboptimal.
Hyperparathyroidism: comparison of MR imaging with radionuclide scanning.
Twenty-three patients with hyperparathyroidism were evaluated preoperatively with magnetic resonance (MR) imaging. Twenty patients also underwent thallium-201/technetium-99m scintigraphy. Of 22 patients with primary hyperparathyroidism, 12 had persistent or recurrent disease. One had secondary hyperparathyroidism due to end-stage renal disease. MR imaging allowed accurate localization of abnormal parathyroid glands in 64% evaluated prospectively and 82% evaluated retrospectively. Scintigraphy allowed localization of 60% evaluated prospectively and 70% retrospectively. The two imaging modalities together allowed detection of 68% evaluated prospectively and 91% retrospectively. MR imaging allowed detection of two of five mediastinal adenomas evaluated prospectively and four of five retrospectively. In patients who underwent both imaging studies, MR was more successful in those with previous neck surgery (73% evaluated prospectively and 91% retrospectively) than in those with no prior surgery (57% prospectively and 71% retrospectively). Scintigraphy allowed accurate localization in 64% evaluated prospectively and 64% retrospectively in patients with previous surgery versus 57% prospectively and 86% retrospectively in patients with no prior neck surgery. Four false-positive results were obtained with MR imaging and three with scintigraphy. MR imaging was useful for parathyroid localization in patients with hyperparathyroidism, particularly in patients requiring additional surgery.
Acute myocardial infarction: MR evaluation in 29 patients.
This study evaluated the ability of MR to identify and characterize the region of myocardial infarction in humans. Twenty-nine patients, all with ECG and enzyme rises consistent with an acute myocardial infarction, were studied by MR 3-17 days from the onset of acute chest pain. Four patients were excluded because of inability to acquire adequate MR studies. For comparison, 20 normal subjects were studied who also had gated MR examinations. The site of infarction was visualized in 23 patients as an area of high signal intensity in relation to the normal myocardium, a contrast that increased on the second-echo image. The regions of abnormal signal intensity corresponded to the anatomic site of infarction as defined by the ECG changes. The mean T2 relaxation time of the infarcted myocardium (79 +/- 22 msec) was significantly prolonged in comparison with the mean T2 (43.9 +/- 9 msec) of normal myocardium (p less than .01). The mean percentage of contrast (intensity difference) between normal and infarcted myocardium was much greater on the second-echo images (65.6 +/- 34.0%) than the first-echo images (27.5 +/- 18.7%). In the normal subjects there was no difference in T2 between the anterolateral (40.3 +/- 5.7 msec) and septal (39.5 +/- 7.4 msec) regions, and percentages of contrast between these two regions of myocardium on the first-echo (9.1 +/- 7.4%) and second-echo (15.0 +/- 13.3%) images were similar. Thus, MR can be used to directly visualize acute infarcts. However, it has several pitfalls, including the necessity to differentiate signal from slowly flowing blood in the ventricle, from increased signal from a region of infarction and artifactual variation of signal intensity in the myocardium due to respiratory motion or residual cardiac motion.
MR imaging of congenital anomalies of the aortic arch.
Eighteen patients with congenital aortic arch anomalies were evaluated by ECG-gated MR imaging. Transverse images encompassing the heart and thoracic aorta were available in all patients; sagittal or coronal studies were available in 12 patients. Visualization of the aortic arch, its orientation, and the origin and course of the arch vessels was assessed. Associated intracardiac abnormalities were noted, and the effect of aberrant vessels on the trachea or esophagus was determined. Thirteen patients had a right aortic arch. Mirror-image branching was found in 10 cases, and an aberrant left subclavian artery was found in three of these. Three patients had a left aortic arch with aberrant right subclavian artery, and two patients had a double arch. Tracheal compression caused by vascular rings was found in two patients with respiratory symptoms. Corroborating studies (angiography, surgery, CT, and autopsy) in 16 patients confirmed the MR diagnoses in all but one. We conclude that MR could substitute for other techniques as an effective, noninvasive method for the evaluation of congenital aortic arch anomalies.
Central thrombi in pulmonary arterial hypertension detected by MR imaging.
Differentiation of thrombi from slow flow in the pulmonary arteries, sometimes observed in the presence of pulmonary arterial hypertension, can be equivocal. Magnetic resonance (MR) imaging was performed in a patient with chronic pulmonary thromboembolism and pulmonary arterial hypertension using an electrocardiographically gated technique that allowed visualization of the pulmonary arteries at the end of diastole and multiple times during systole. These images were compared with those of a patient with primary pulmonary hypertension and those of healthy subjects. Thrombi were discrete structures, seen throughout the cardiac cycle on both the first and second spin-echo images, and decreased in signal intensity on the second image. Slow flow increased in signal intensity and changed in structure during the cardiac cycle and was seen best on the second image. MR may play an important role in excluding large central thrombi as the cause of pulmonary arterial hypertension. It is a noninvasive method for defining pulmonary arterial wall thickness and for direct visualization of chronic pulmonary thrombus.
Congenital heart disease: gated MR imaging in 72 patients.
Seventy-two patients (aged 2 months to 75 years; mean 23 years) with a variety of congenital anomalies of the heart and great vessels underwent ECG-gated magnetic resonance (MR) imaging using the multisectional spin-echo technique (0.35 Tesla). The ability to define segmental anatomy and intracardiac anomalies on transverse, sagittal, and coronal images was evaluated. MR images were graded as excellent, diagnostic, or nondiagnostic, and MR findings were corroborated by angiography and/or two-dimensional echocardiography. Studies that were considered to be excellent or diagnostic were obtained in 96% of the cases. Visceroatrial situs, the type of ventricular loop, and the relationship of the great vessels could be identified in all patients with studies encompassing the entire heart. Forty-four of 47 abnormalities at the level of the great vessels were identified with MR, including coarctation of the aorta and vascular rings. MR showed 32 of 35 ventricular abnormalities; 2 small ventricular septal defects and 1 Ebstein anomaly were not demonstrated. All of the abnormalities at the atrial level and those of systemic and pulmonary venous return were seen on MR images. Complex cardiac anomalies, such as single ventricles, and the status of the pulmonary arteries were clearly demonstrated, and a good assessment of total and palliative postoperative anatomy was provided.
Cholecystitis: detection with MR imaging.
The role of magnetic resonance (MR) imaging in the detection of gallbladder disease was evaluated in 39 individuals (16 healthy, five with asymptomatic gallstones, and 18 with clinical symptoms of gallbladder disease). MR imaging was performed after they fasted for 12 hours. Imaging sequences included a combination of repetition times (TR) of 0.5 and 1.5 sec and echo times (TE) of 28 and 56 msec. On the images obtained at TR = 0.5 sec and TE = 56 msec, gallbladder bile was hyperintense compared with the liver in all healthy and asymptomatic subjects and was hypointense (n = 9), isointense (n = 4), or hyperintense (n = 5) in symptomatic patients, eight of whom had surgical confirmation of cholecystitis. Comparison of normal versus pathologically proved cases for the presence of gallbladder disease yielded a specificity of 100%, sensitivity of 75%, and a significant difference of P less than .01. Thus, with a pulse sequence of TR = 0.5 sec and TE = 56 msec, MR was sensitive in detecting gallbladder disease. However, the role of MR in the radiologic workup of gallbladder disease will be determined by more experience with this modality.
Uterine leiomyomas: correlation of MR, histopathologic findings, and symptoms.
Magnetic resonance (MR) imaging, symptoms, and pathologic findings were correlated in 59 uterine leiomyomas from 23 patients. The tumors varied from less than 1 cm to 18 cm in diameter. Fifty-seven leiomyomas were identified in the corpus uterus, one was located within the broad ligament, and another was detected in the cervix. Among the corpus lesions, 9 were correctly identified on MR images as subserosal and 37 as intramural. Of 11 tumors assigned at surgery to the submucosal group, 10 had been accurately defined with MR. On MR, myomas associated with hypermenorrhea produced an anatomic disruption of the "junctional zone" (the low-intensity band seen at the myometrium-endometrium junction on T2 contrast images). Long TR (2 sec) and TE (56 msec) parameters (T2 contrast images) yielded the best contrast resolution between leiomyoma and surrounding myometrium. Correlation of MR with histologic features demonstrated 2 groups of lesions. Leiomyomas free of degenerative changes emitted homogeneous signals of low intensity. Contrast between tumor and myometrium was -16% on the T1 contrast image and increased to -44 +/- 16% on the T2 contrast image. Leiomyomas with hyaline, myxomatous, or fatty degeneration demonstrated various degrees of inhomogeneity, best seen on images obtained with long TR and TE. It is concluded that MR is an accurate modality for imaging uterine leiomyomas, since it clearly demonstrates tumor number, size, location, and the presence and extent of degeneration.
MR imaging of the dilated biliary tract.
The magnetic resonance (MR) examinations of 18 patients with dilated bile ducts were reviewed retrospectively to determine the capability of MR to demonstrate biliary dilatation, assess MR appearance of the dilated biliary tract using spin-echo techniques, and define the optimal MR imaging parameters (repetition time [TR] and echo time [TE]) for its demonstration. On images with short TR (0.5 sec) and TE (28 msec), the dilated intrahepatic and intrapancreatic bile ducts usually had lower signal intensity compared with the surrounding liver or pancreas; on images with long TR (2.0 sec) and TE (56 msec), they had higher signal intensity. Because of the observed variation in percentage of contrast between dilated bile ducts and surrounding liver and pancreas, two imaging sequences are recommended to obtain reliable demonstration of dilated intrahepatic and intrapancreatic bile ducts. The dilated common bile duct at the level of the hepatic hilus is best seen with a short TR and TE.
Coarctation of the aorta: MR imaging.
Thirteen patients, aged 3-31 years, with coarctation of the thoracic aorta were examined by magnetic resonance (MR) imaging (total of 14 studies). Eight studies were performed preoperatively and six postoperatively. Catheterization data were available on 12 patients for verification of MR imaging findings. Electrocardiographically gated sagittal and left anterior oblique images best depicted the coarctations; however, involvement of arch vessels was best evaluated on transaxial images. MR imaging readily identified all coarctations but one, their site and extent, and involvement of the arch vessels. In addition, MR images depicted poststenotic dilatation and dilated collateral vessels. In patients studied postoperatively, restenosis could be evaluated, and complications such as postoperative aneurysm and perianastomotic hematoma were identified. MR imaging provides excellent anatomic detail of coarctation of the aorta, potentially obviating the need for angiography.
Gestational trophoblastic neoplasm of the uterus: MR assessment.
Magnetic resonance (MR) imaging characteristics of uterine gestational trophoblastic neoplasia were prospectively studied in nine women (aged 21-58 years). MR imaging was done at the time of initial clinical diagnosis, after each of the first two cycles of chemotherapy, and 6-9 months after initiation of chemotherapy. Sagittal and transverse MR images of the pelvis were generated with a 0.35-T superconducting magnet and the double spin-echo technique with short and long repetition times (TRs). The neoplasm distorted the MR appearance of uterine zonal structures (myometrium, endometrium, and junctional zone) and demonstrated hypervascular masses of heterogeneous signal intensity. Favorable response to chemotherapy was determined by a decrease in serum beta-subunit human chorionic gonadotropin (HCG) concentrations, and was accompanied by MR findings of regression of vascular abnormalities, development of intralesional hemorrhage, and return of normal appearance of uterine zones. The return of uterine zonal anatomy on MR images antedated definitive decrease in uterine volume. All eight patients imaged 6-9 months after initial imaging showed normal uterine volume and zonal anatomy.
MR imaging of the thyroid.
The thyroid gland was evaluated with MR imaging in six normal subjects and 32 patients with thyroid disease. The purpose was to evaluate signal characteristics of normal and diseased thyroid tissue; determine the contrast between normal and diseased tissue on T1- and T2-weighted images; compare relaxation times of normal thyroid, adenomas, and carcinoma; and assess the capability of MR for showing the extent of large thyroid masses. Adenomas and carcinomas were frequently isointense with normal thyroid tissue on T1-weighted images but had markedly higher intensity on T2-weighted images. The mean T1 (1202 +/- 717 msec) and T2 (118 +/- 48 msec) relaxation times of adenomas were markedly longer than the T1 (721 +/- 97 msec) and T2 (59 +/- 10 msec) times of normal thyroid tissue. Likewise, the T1 and T2 values of carcinomas were markedly prolonged compared with normal thyroid but the values overlapped with those of the adenomas. Sagittal and coronal images effectively depicted the extent of large goiters, adenomas, and carcinomas and indicated extension below the cervicothoracic junction. The marked prolongation of relaxation times associated with thyroid disease causes excellent contrast of lesions with normal thyroid and surrounding structures. The large field of view possible with coronal and sagittal images is useful for assessing extensive thyroid masses. These attributes indicate the potential clinical utility of MR for evaluating thyroid disease.
Imaging of septic arthritis.
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Gynecologic masses: value of magnetic resonance imaging.
Forty-two women with gynecologic abnormalities were studied with the use of magnetic resonance imaging. Magnetic resonance imaging correctly assessed the origin of the pelvic mass in all patients. In the evaluation of leiomyoma, magnetic resonance imaging accurately depicted the number, size, and location of the lesion. In the evaluation of endometrial carcinoma, magnetic resonance imaging depicted the location of the lesion, the presence of cervical extension, and the depth of myometrial penetration in the majority of the cases. In the analysis of adnexal cysts, magnetic resonance imaging was sensitive in localizing the lesion and was able to distinguish serous from hemorrhagic fluid. This preliminary report indicates that magnetic resonance imaging may become a valuable imaging modality in the diagnosis of gynecologic abnormalities.
Present clinical status of magnetic resonance imaging.
Magnetic resonance imaging has achieved clinical importance and has become the primary tool in the investigation of head, spinal cord, pelvis, cancellous bone, pericardium (with gating), gallbladder, lymph node masses, and very soon, in the evaluation of joints. In many areas, particularly with respiratory and ECG gating, this method promises to replace all other imaging modalities with the precision of information obtained. Today the exceptions are the alimentary tube and its mesentery, between the esophagus and rectum, and the peripheral lung.