A. Everette James

Sonography of the endometrium during conception and nonconception cycles of in vitro fertilization and embryo transfer

The thickness of the endometrium was compared in 15 patients who conceived and 15 who did not with an in vitro fertilization and embryo transfer (IVF-ET) protocol after ovulation induction with human menopausal gonadotropin/human chorionic gonadotropin (hMG/hCG). There was no statistically significant difference (P = 1.0) in the endometrial thickness in the conception versus the nonconception group. Average estradiol (E2) values and number of mature follicles were also not statistically different in the two groups (P = 0.78, P = 0.81). There was a slightly significant difference in the number of embryos transferred in the conception versus nonconception groups (2.5 versus 1.9, P = 0.005). However, the most significant difference between the conception and nonconception groups was the total number of oocytes retrieved (4.4 versus 2.8, P = 0.005). These findings indicate that there are no sonographically detectable differences in the endometrial thickness in patients who achieve pregnancy versus those that do not when given a similar ovulation induction regimen of hMG/hCG for IVF-ET.

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.

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.

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.

Digital image motion correction by spatial warp methods.

A technique for correction of motion between images which are obtained in high-speed digital subtraction or cine angiographic acquisitions is being tested. The method is based on the application of quadratic polynomial equations which transform one image so that it matches a reference image. Images which have been processed in this manner can be summed to improve the signal-to-noise ratios over individual images. The technique for motion correction currently being tested uses operator interaction to establish the appropriate polynomial transformation. An operator selects fiducial (reference) points on an image which will be the reference. Then he selects the corresponding fiducial points on the image to be processed. The algorithm calculates the coefficients of a pair of quadratic polynomial equations and applies them to each pixel in the image. Results demonstrate the application of the technique in phantoms and in digitized cine angiograms.

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.

Primary glioma: diagnosis with magnetic resonance imaging

Seventeen patients with surgically documented primary glial-origin brain tumors were evaluated by magnetic resonance imaging and high-resolution computed tomography. The exclusion of CT ring-enhancing lesions directed the focus of this study toward lower grade tumors that were more difficult to diagnose. The computed tomography abnormalities were often subtle and included areas of low attenuation, mass effect, and focal enhancement. Spin-echo sequences with both heavy T1 and T2 weighting were utilized. Prolonged T1 and T2 values were observed in all tumors. The T2-weighted spin-echo 1000/120 sequence was the most sensitive in tumor detection and was positive in all cases. Magnetic resonance imaging was superior to computed tomography in tumor detection, tumor localization, assessment of tumor extent, and determination of associated changes, ie, brain stem encroachment. All the magnetic resonance sequences used showed an increase in severity of imaging changes with increasing tumor grade. The T2-weighted sequence showed progressive margin irregularity, whereas the T1-weighted (inversion recovery) sequence showed increasing severity of internal tissue changes. The superior resolution of these changes by magnetic resonance imaging may have implications for better assessment of tumor grade in the future than is currently possible with computed tomography.

A critique of the concept of MRI centers

A significant proportion of MRI units are being installed in MRI Centers that are free standing enterprises offering outpatient diagnoses separate from hospitals. The development of such Centers represents a challenge to more traditional arrangements and may have serious implications for physician responsibility that depend on their management and administration. In this review several legal and ethical issues arising from the proliferation of such Centers are analyzed and it is argued that regulatory attitudes may need to be altered to avoid major shifts of emphasis in the pattern of use of high cost imaging equipment.

A Technique For Automatic Motion Correction In DSA

The motion of the contracting heart has made it impossible to study coronary arteries with venous injections of contrast using digital subtraction angiography (DSA), even with cardiac gating. Furthermore, for intravenous injections, the images are statistically very poor due to the small size of the vessels and dilution of the contrast media, rendering the images diagnostically useless. A technique based on polynomial transformations has been implemented and is being evaluated which permits removal of motion between a pair of images acquired during mask-mode DSA. This technique is capable of handling three-dimensional motion and is based on applications of techniques of fluid dynamics, statistical sampling theory, and artificial intelligence. A series of phantom images, exhibiting three dimensional motion, are shown which demonstrate the ability of the technique to remove motion.

Medical image management: practical, legal and ethical considerations.

The data acquired by the new medical imaging techniques, in many ways, exceeded our ability to properly store, transmit and use the images produced. As diagnostic imaging procedures become progressively less invasive and traumatic, they are being applied to a much larger patient population. The decrease in memory and other instrumentation costs, along with expanded technological capability of computer systems, has provided medicine an opportunity to create network systems for the storage, processing, recall, and remote location of these diagnostic images. Therefore, problems of access and confidentiality have become increasingly important. This communication will consider certain medical, legal, and ethical aspects of these technologies of data acquisition, storage, manipulation and retrieval.