Important considerations in measurement of attractive force on metallic implants in MR imagers

Almost all reported measurements of the attractive force exerted on metallic implants in magnetic fields of magnetic resonance imagers have been obtained at the portal. This study was done to determine whether the maximum force on an implant is at the portal. Horizontal attractive forces on needles were measured along the axis of the bore at various distances from the portal of a 0.3-T vertical-field magnet and 0.5- and 1.5-T solenoid magnets. Upward vertical forces along the top of the bore were also measured. The horizontal forces 40 cm in from the portals of the 0.5- and 1.5-T magnets were 70%-80% greater than the horizontal forces at the portal. The upward vertical force at the top of the 0.3-T magnet bore, 63 cm in from the portal, was 20 times the horizontal force at the portal and was twice the maximum force measured in the 0.5-T magnet. The maximum force was not at the portal.     

Diabetes regimen behaviors. Predicting adherence

In this study, Social Learning Theory was used to generate psychosocial predictors of regimen adherence among persons with insulin-dependent diabetes mellitus (IDDM). Four categories of predictors were formed: knowledge, expectancies, skills, and environmental support. Persons with IDDM (84 adults and 23 adolescents) completed measures within each predictor category on two occasions, separated by 6 months. Multimethod assessment procedures (self-monitoring, interviews, mechanical devices) were used to measure adherence to four aspects of the IDDM regimen: insulin injections, glucose testing, diet, and exercise. Bivariate analyses demonstrated that measures of expectancies and environmental support were reliably related to several adherence behaviours. In particular, self-efficacy expectations were related to adherence across almost all regimen areas for both adolescents and adults. Skills were also important, though only for adolescents, whereas regimen knowledge was unrelated to adherence for either adults or adolescents. Multivariate analyses showed that expectancies were consistently predictive of adherence and that, in general, psychosocial variables were better predictors of insulin administration and glucose testing than of diet or exercise. The implications of these findings for diabetes education programs are discussed.     

Cytological grading of prostatic aspiration biopsy: a comparison with the Gleason grading system

Cytological grade determined by fine needle aspiration of the prostate was compared to histological grade in 30 patients undergoing subsequent radical prostatectomy. The degree of cytological pleomorphism determined by the consensus grade of 3 observers predicted correctly the Gleason grade sum range in 80 per cent of the cases. The cytological grade was reasonably reproducible with agreement among all 3 observers in 50 per cent of the cases and between 2 of 3 observers in the remainder. The accuracy of predicting the Gleason grade sum of the radical prostatectomy specimen by cytological examination compared favorably with that achieved by histological examination of cutting needle biopsy and transurethral resection specimens reported in the literature.     

Use of radio-frequency field gradients to image blood flow and perfusion in vivo

A magnetic resonance imaging method based on the use of radio-frequency (RF) magnetic field gradients to detect molecular motion has been combined with GRASS (gradient-recalled acquisition in a steady state) imaging to detect arterial blood flow in vivo. The method has been used to selectively attenuate signals from flowing blood in the human finger. Attenuation of signals from arterial blood was greatly reduced when blood flow was decreased with the application of a tourniquet. This result demonstrated the sensitivity of the technique to the rate of blood flow. RF gradient coils can be used to generate very high RF gradients with submicrosecond rise times and minimal eddy currents. Therefore, this method may prove useful for imaging very slow, nonuniform flow through capillary beds and in the extravascular space.     

Incorporation versus infection of retroperitoneal aortic grafts: MR imaging features

The magnetic resonance (MR) imaging characteristics of normal aortic graft healing were compared with those of perigraft infection in 57 patients after aortic graft implantation. Thirty-three patients without postoperative complications underwent MR imaging in a 0.35-T unit 1 week after graft implantation, and 13 of those patients were reexamined 2-3 months after graft implantation. Twenty-four patients with clinically suspected perigraft infection underwent MR imaging 6 weeks to 18 years after graft implantation. Early normal postoperative changes were characterized by a perigraft collar of low to medium signal intensity on T1-weighted images and of high intensity on T2-weighted images in all 33 cases, consistent with perigraft fluid collection. In 10 of 13 patients reexamined 2-3 months postoperatively, the MR images demonstrated a collar of tissue consistent with perigraft fibrosis. In cases of clinical suspicion of retroperitoneal graft infection, MR imaging showed eccentric fluid collections of low to medium signal intensity on T1-weighted images and high intensity on T2-weighted images at more than 3 months after surgery. The MR findings were diagnostic of retroperitoneal perigraft infection in 17 of 20 patients shown to be infected at surgery. Retroperitoneal infection was correctly excluded on the basis of MR findings in four patients. Thus, MR imaging is an accurate imaging method for the diagnosis of aortic graft infection. In the early postoperative phase, resolving perigraft fluid cannot be differentiated from perigraft infection.     

Neuropathologic findings in the acquired immunodeficiency syndrome (AIDS)

The acquired immunodeficiency syndrome (AIDS) is characterized by a severe idiopathic deficiency in T-cell mediated immunity. Homosexuals, intravenous drug abusers and Haitians are predominantly affected, predisposing them to opportunistic infections and neoplasms. In this study, the central nervous system (CNS) was examined at autopsy in 29 AIDS patients. Significant CNS complications occurred in 55%, mainly related to opportunistic infections similar to those seen in patients with other causes of immunosuppression. Progressive multifocal leukoencephalopathy (three cases), cytomegalovirus (CMV) encephalitis (five cases), cryptococcal meningitis (four cases), Mycobacterium avium-intracellulare (three cases), and toxoplasmosis (one case) were found. Widespread microglial nodules were observed in 20 patients, 80% of whom had CMV inclusions elsewhere at autopsy. Primary cerebral lymphoma (one case) and lymphomatoid granulomatosis (one case) were present. Subarachnoid (five cases) and intraparenchymal (three cases) hemorrhage was seen although these were not usually clinically significant. A single case of embolic arterial obstruction with cortical infarction was due to non-bacterial thrombotic endocarditis.     

A controlled study of a standardized behavioral stepped treatment for hypertension

A standardized behavioral stepped care (SC) treatment for hypertension (blood pressure monitoring followed by self-administered systolic blood pressure biofeedback and relaxation, in sequence, as needed) was administered to 51 patients whose blood pressures were medically controlled to within normal limits. The effects of treatment upon blood pressure, medication requirements, and cost of care were compared with those of 51 referred care (RC) control patients who continued their usual care for hypertension. SC and RC patients were matched in groups on the basis of medication requirements (Group I, diuretics; Group II, beta-blockers alone or with a diuretic; and Group III, vasodilators alone or with a drug from Group I or II). The duration of the SC procedure was 1, 4, or 7 months--as necessary--and the follow-up period was 12 months. The RC protocol lasted 19 months. Medication requirements for SC patients declined to levels significantly (p less than 0.05) lower than those of RC patients from the biofeedback phase throughout follow-up for all drug groups combined. However, when the drug groups were analyzed separately, this was true for Groups I and II only. Similarly, the cost of care for all drug groups combined was lower for SC patients from the biofeedback phase through 9 months of follow-up, also reflecting changes seen in Drug Groups I and II only. Blood pressure levels remained controlled, in all groups, throughout the investigation. Clinical possibilities for combined behavioral and pharmacological treatment of hypertension are discussed relative to the pathophysiology of hypertension, and questions for future research are suggested.     

Delayed effects of ionizing radiation on the ear

The question of damage to the ear from exposure to ionizing radiation was addressed by exposing groups of chinchillas to fractioned doses of radiation (2 Gy per day) for total doses ranging from 40 to 90 Gy. In order to allow any delayed effects of radiation to become manifest, the animals were sacrificed two years after completion of treatment and their temporal bones were prepared for microscopic examination. The most pronounced effect of treatment was degeneration of sensory and supporting cells and loss of eighth nerve fibers in the organ of Corti. Damage increased with increasing dose of radiation. The degree of damage found in many of these ears was of sufficient magnitude to produce a permanent sensorineural hearing loss.