The lawyer's perspective on the use of ultrasound in obstetrics and gynecology

Diagnostic sonography, also known as ultrasound, has become an invaluable aid in the practice of obstetrics and gynecology. Rapid improvements in instrumentation have caused the sonologist and sonography to assume a primary role in the care of these patients. Patient and physician expectations have increased with the technological advances. This paper will outline the advances and capabilities of diagnostic sonography in obstetrics and gynecology, while reflecting upon the foreseeable legal implications.

The physics of ultrasound is rather complex. Briefly, ultrasound utilizes high-frequency, non-ionizing, mechanical waves, 2.25 to 10 megahertz, that require a molecular medium for propagation. The reflected energy is processed to produce an image. Because it employs non-ionizing waves, ultrasound is considered safe by most authorities when used at the intensities currently employed for diagnosis. No clinically significant adverse effects have been reported in humans to date.

Clinical magnetic resonance imaging with nuclear medicine correlation

The current role of magnetic resonance imaging (MRI) in different organ systems is discussed and compared to nuclear medicine and to other available clinical diagnostic modalities. The value of optimizing radiofrequency pulse sequence selection to provide additional tissue characterization is also described. The results of nuclear medicine and MRI studies in 56 patients are compared to evaluate the clinical diagnostic contribution of each imaging modality for various pathological processes. In addition, the state-of-the-art MRI systems and future development in MRI technology with its potential contribution is defined.

Antitrust aspects of exclusive contracts in medical imaging

Exclusive contracts between radiologists and hospitals may be more frequently scrutinized for antitrust violations because of the Hyde v Jefferson Parish Hospital District No. 2 case. In the Hyde case, the lower court decided antitrust law had been violated, and it was the first antitrust case about exclusive medical contracts to be reviewed by the U.S. Supreme Court. The case is a precedent for considering similar circumstances according to traditional business antitrust analyses such as per se violations, tying arrangements, group boycott, and market foreclosure. Areas that may be scrutinized for anticompetitiveness include hospital privileges when radiologists have exclusive contracts with the community's only hospital or provide services unique within an area, and physicians' access to scarce resources (e.g., computed tomography [CT], magnetic resonance [MR] imaging). Radiologists must understand antitrust implications of their hospital contracts; examine the terms of staff appointment, bylaws, and rights; and be able to guide their attorneys through contract negotiations.

Uterine adnexal torsion: sonographic findings

Acute torsion of the uterine adnexal structures (ovary and fallopian tube) is a recognized surgical emergency, but rarely has the diagnosis been made preoperatively on the basis of imaging studies. This report describes 16 cases in which the diagnosis was suggested preoperatively on the basis of sonography and subsequently confirmed at surgery. In all of the patients studied, a pelvic or pelvoabdominal mass was present on sonography. These masses had a sonographic texture ranging from cystic to solid, depending on the presence and extent of internal hemorrhage and/or stromal edema. In the majority of patients (13 of 16), adnexal torsion was associated with a preexisting cystic adnexal mass. Eight of these had thin internal septae. The severity of symptoms was variable and did not correlate directly with the sonographic features of the pelvic mass. Consideration of this entity in the proper clinical setting and with the typical sonographic findings will facilitate prospective recognition of adnexal torsion, thereby improving the chances for salvage of the involved adnexal structures.

111In-labeled eosinophils: localization of inflammatory lesions and parasitic infections in mice

Based upon recent development of practical isolation techniques for eosinophils, labeling and in vivo imaging of eosinophils has been achieved. Isolation of cells was performed utilizing a Percoll density gradient. The eosinophils were subsequently labeled by a modified 111In-oxine method. Migration of eosinophils in response to intradermal ear-pinna injections of SEA (soluble schistosoma egg antigen), S. mansoni eggs, E. coli, and turpentine was followed with gamma-ray camera imaging from 4 to 48 h. Maximal localization, determined by Gamma 11 data processing, occurred by 4-h post-injection of radiolabel. SEA and S. mansoni eggs provided a greater stimulus for localization than E. coli or turpentine. Neutrophils did not preferentially accumulate. Tissue distribution of labeled eosinophils was greatest in the spleen, followed by liver and bone. 111In-labeled-eosinophil scans are sensitive to parasitic infections, although somewhat nonspecific.

The use of Gd DTPA as a perfusion agent and marker of blood-brain barrier disruption

To provide contrast enhancement in magnetic resonance imaging, a new class of compounds has been developed, the paramagnetic metal ion chelates. Gadolinium (Gd) DTPA, a prototype of this class, shows a sufficiently high in vivo stability and low toxicity for use in initial clinical trials. This type of agent, designed for rapid clearance by glomerular filtration, allows the assessment on MRI of renal function, alterations in tissue perfusion, myocardial ischemia, and perhaps most significantly disruption of the blood-brain barrier (BBB). Research at Vanderbilt has demonstrated these applications, with particular emphasis in three areas. Tissue perfusion changes, such as those produced by ligation of the arterial blood supply to portions of the spleen and kidney, cannot easily be detected on unenhanced MRI. These acute tissue infarcts can be readily identified following the administration of Gd DTPA. The question of field strength dependence of Gd DTPA has been addressed by experimentation at 0.15, 0.5, and 1.5 tesla. Furthermore, the ability to detect an alteration of the BBB, when present without associated edema, has been demonstrated with the application of control enhancement. The use of contrast agents in MRI will enhance both the sensitivity and specificity of magnetic resonance imaging.

Particulate oral NMR contrast agents

Insoluble paramagnetic compounds in suspension can be used to achieve visualization of the gastrointestinal system on magnetic resonance imaging (NMR). Particulate preparations of these agents decrease the T1 and T2 of solutions to which they are added. Gadolinium oxalate, a prototype of these particulate agents, was evaluated in vitro and in vivo (in rabbits) by NMR imaging. The effect of this compound upon T1 and T2 in vitro was also quantitated by NMR spectroscopy. Opacification of the upper gastrointestinal tract was achieved with gadolinium oxalate following oral administration. The colon was visualized following rectal administration.

Dyke Award. Evaluation of contrast-enhanced MR imaging in a brain-abscess model

An alpha-streptococcus brain abscess was produced in five dogs and studied with magnetic resonance (MR) imaging (0.5 T) and computed tomography (CT). Non-contrast- and contrast-enhanced CT scans were obtained using gadolinium diethylenetriamine-pentaacetic acid (Gd DTPA) for MR imaging and meglumine iothalamate for CT scanning. Each animal was evaluated in the early and later cerebritis stages of abscess evolution. On MR, the area of cerebritis enhanced after administration of Gd DTPA in a manner similar to that observed with contrast-enhanced CT. However, contrast enhancement was greater on the MR examination. Early lesions in two animals were detected only with contrast-enhanced MR imaging. This experience suggests that intravenously administered agents such as Gd DTPA should increase the diagnostic potential of MR imaging in neurologic diseases, especially those altering the blood-brain barrier.

Initial clinical evaluation of gadolinium DTPA for contrast-enhanced magnetic resonance imaging

Gadolinium DTPA was evaluated as an intravenous contrast agent for magnetic resonance imaging in 15 patients with primary or secondary intracranial neoplastic disease. T1 and T2 weighted images were obtained prior to contrast administration. T1 weighted spin echo 35/800 (TE/TR) images were utilized to detect enhancement. The increase in signal intensity observed, identifying areas of breakdown of the blood-brain barrier (BBB), was similar in magnitude to the contrast enhancement observed on CT. This permitted differentiation of neoplastic tissue from surrounding cerebral edema on MRI. Direct visualization of otherwise "isomagnetic" lesions was also demonstrated. The use of intravenous contrast media should significantly extend the diagnostic potential and specificity of magnetic resonance imaging.

Gated magnetic resonance imaging of acute myocardial ischemia in dogs: application of multiecho techniques and contrast enhancement with GD DTPA

ECG gated magnetic resonance images were obtained in six canines prior to and immediately following occlusion of either the LAD or circumflex coronary artery using a surgically placed snare. Multiecho and single-echo acquisition techniques were utilized 0.25 mmol/kg Gd DTPA was injected as an IV bolus 1 hr following coronary artery ligation. In two animals, the region of ischemic myocardium was clearly visualized on multiecho technique without the use of intravenous contrast. The ischemic zone could be best identified on images with a long TE of 120 msec. Contrast enhancement with Gd DTPA enabled visualization of the ischemic myocardium in all six canines. Administration of Gd DTPA, a perfusion agent, improved both detectability and definition of the myocardial lesions.

Current perspectives on medical imaging

Advances in biomedical technology have expanded the potential of medical imaging. Selected aspects of developments in sonography, nuclear medicine, nuclear magnetic resonance and digital imaging are addressed, stressing the wide scope permitted by these newer modalities.

Magnetic resonance imaging of multiple sclerosis: a study of pulse-technique efficacy

Forty-two patients with the clinical diagnosis of multiple sclerosis were examined by proton magnetic resonance imaging (MRI) at 0.5 T. An extensive protocol was used to facilitate a comparison of the efficacy of different pulse techniques. Results were also compared in 39 cases with high-resolution x-ray computed tomography (CT). MRI revealed characteristic abnormalities in each case, whereas CT was positive in only 15 of 33 patients. Milder grades 1 and 2 disease were usually undetected by CT, and in all cases, the abnormalities noted on MRI were much more extensive than on CT. Cerebral abnormalities were best shown with the T2-weighted spin-echo sequence (TE/TR = 120/1000); brainstem lesions were best defined on the inversion-recovery sequence (TE/TI/TR = 30/400/1250). Increasing TE to 120 msec and TR to 2000 msec heightened the contrast between normal and abnormal white matter. However, the signal intensity of cerebrospinal fluid with this pulse technique obscured some abnormalities.

Intravascular contrast agents suitable for magnetic resonance imaging

Two paramagnetic chelates, chromium EDTA and gadolinium DTPA, were evaluated as potential intravenous contrast agents for magnetic resonance imaging (MR) using a 0.5-T superconducting scanner. After evaluating both agents in vitro, in vivo studies were conducted in dogs to document changes in renal appearance produced by contrast injection. Acute splenic and renal infarction were diagnosed with contrast-enhanced MR and confirmed by gamma camera imaging following administration of Tc-99m-labeled DMSA and sulfur colloid. The authors conclude that intravenous paramagnetic contrast agents presently offer the best mechanism for assessment of tissue function and changes in perfusion with MR.

Evaluation of renal masses by MR imaging

Magnetic resonance (MR) imaging was performed in 20 subjects, 10 of whom had benign or malignant renal masses, and 10 were normal volunteers. The purpose of the study was to evaluate the ability of MR to provide significant diagnostic information in the management of renal mass lesions. Ten normal patients were included to supply baseline data. Different pulse sequences were used and their contribution to the diagnosis was evaluated. The emphasis has been placed on evaluating MR against the pathological diagnosis rather than other imaging modalities.

Paramagnetic NMR contrast agents. Development and evaluation

Paramagnetic ions could be theoretically used as NMR contrast agents because of their effect upon T1. However, the toxicity of these ions prevents their application. By the formation of appropriate chemical complexes with these ions, the toxicity of these agents can be substantially reduced while maintaining the paramagnetic effect. Two potential NMR contrast agents, one for oral use and one for intravenous administration, were developed and evaluated both in vitro and in vivo. The effect upon T1 in vitro of these paramagnetic compounds was determined using a JEOL FX-90Q NMR spectrometer. These agents were evaluated in vivo in dogs with a Technicare 0.3 tesla superconducting magnet system and in rabbits with the Aberdeen 0.04 tesla resistive NMR imager. Using calculated T1 NMR images, a nontoxic dose of gadolinium oxalate provided visualization of the gastrointestinal tract. Intravenous administration of chromium EDTA provided enhancement of the kidneys, ureters, and bladder, thereby potentially allowing for the evaluation of renal function with magnetic resonance imaging. Stable paramagnetic complexes can serve as effective, nontoxic, oral and intravenous NMR contrast agents.

Patient risk from interproximal radiography

Computer simulation methods for determining patient dose from dental radiography have demonstrated that patient risk from a two-film interproximal examination ranges from 1.1 X 10(-8) to 3.4 X 10(-7) using 90-kVp beams, depending on film speed, projection technique, and age and sex of the patient. Further, changing from a short-cone round-beam to a long-cone technique with rectangular collimation reduces risk by a factor of 2.9, independent of other factors.

Sonographic depiction of endometrial changes occurring with ovulation induction

Endometrial thickness and texture were evaluated with serial pelvic sonograms in ten normal, menstruating women and 107 patients undergoing ovulation induction for in vitro fertilization. Serial sonograms were performed in the control group every other day throughout the menstrual cycle, whereas the sonographic examinations of the ovulation induction patients were performed daily in a four- to eight-day time interval after their medications were completed and prior to laparoscopy for follicular aspiration. Endometrial thickness increased (defined as a persistent change greater than or equal to 1 mm) in 21 of 53 women (40 percent) who received human menopausal gonadotropin (HMG). Of the 54 women treated with clomiphene citrate (CC), five of 12 (42 percent) at 50 mg daily, 13 of 33 (39 percent) at 100 mg daily, and one of nine (11 percent) at 150 mg daily were found to have endometrial thickening. Although the frequencies of endometrial thickening in the high-dose CC and HMG groups were not significantly different (P = 0.09), the peak estradiol (E2) levels in the CC (150 mg) group (E2 = 944 +/- 165 pg/ml) were significantly higher (P less than 0.001) than those in the HMG group (E2 = 584 +/- 26 pg/ml). The relatively low frequency of endometrial thickening in women receiving CC (150 mg) despite very high E2 levels, and the decreased incidence of endometrial thickening relative to increasing dosages of CC may reflect an antiestrogenic effect of CC on the endometrium. In those patients undergoing ovulation induction, the texture of the endometrium remained the same in 98 cycles and changed during nine.(ABSTRACT TRUNCATED AT 250 WORDS)

Contrast enhancement of magnetic resonance images by chromium EDTA: an experimental study

Chromium EDTA was evaluated as an intravenous contrast agent for magnetic resonance (MR) imaging in vitro and in vivo in rabbits and rats. The effect of Cr EDTA on T1 and T2 values in vitro was first quantitated by spectroscopy at 2.5 MHz, followed by animal trials in which the effects of intravenous injection of Cr EDTA on calculated T1 MR images (obtained by the spin- warp technique at 1.7 MHz) were determined. Following administration of chromium EDTA, differences in T1 values between normal and abnormal kidneys were noted, renal hydronephrosis and renal ischemia were readily identified by the pattern of change in T1, and changes were observed in the normal rabbit brain and in tumors implanted in rats. It is concluded that the use of stable paramagnetic metal ion chelates, such as Cr EDTA, as intravenous contrast agents in MR imaging is feasible and that such agents would make possible the observation of tissue vascularity, breakdown of the blood-brain barrier, and renal function.

Facility report. Department of Medical Imaging and Radiological Sciences at Vanderbilt University

This department is presented as an academic prototype to meet the health care and research challenges of the next decade. Composed of four separate divisions (diagnostic radiology, radiation oncology, nuclear medicine, radiologic sciences) with appropriate sections, it is organized according to the concept of an integrated basic science-service facility.

The core curriculum in diagnostic radiology residency training

THE CONSTRUCTION of a core curriculum in diagnostic radiology, medical imaging and radiological sciences requires an understanding of the historical context in which the current technological advances of the last two decades are seen in the perspective of traditional radiology. The future trainee in this discipline will require an additional background in physics, engineer ing and computer sciences as well as in-depth clinical kills in the basics of diagnostic imaging. The formula tion of future training programmes must provide appropriate experience in the newer imaging modali ties, such as computed tomography, real time ultra sound, digital radiology, nuclear magnetic resonance and positron emission tomography by building on a broad and complete foundation of core subjects. This communication will discuss a suggested core curriculum from the aspect of the desired results of the prog ramme.

Respiratory gating in magnetic resonance imaging at 0.5 Tesla

A device for gating the acquisition of magnetic resonance images with chest wall motion was developed, and the effects of respiratory gating upon image quality were studied. Images of respiratory gated examinations were compared with those of ungated examinations in 16 subjects. In a subset of four of those subjects, combined respiratory and cardiac gated images were obtained. Respiratory gating removed gross motion artifacts from magnetic resonance images of the chest and abdomen. Resolution of small normal tissue structures, such as the portal and hepatic veins, is improved. In cardiac studies, respiratory gating improved the visualization and definition of the atria and ventricles.