Magnetic resonance imaging of the adrenal glands

Although CT should be used as the initial procedure, MRI potentially can identify most adrenal masses without the hazard of ionizing radiation or the injection of iodinated contrast material.

Myometrial invasion by endometrial carcinoma: sonographic assessment

The depth of myometrial invasion by endometrial carcinoma was evaluated using real-time sonography (US) in 20 patients with histologically proved adenocarcinoma of the endometrium. In 14 of 20 (70%) cases, US-based estimation of the depth of myometrial invasion was within 10% of the actual measurement in the gross specimen. The US-based estimation of tumor invasion was low in seven patients, high in four patients, and agreed with pathologic findings (+/- 5%) in nine patients. In four patients with polypoid intraluminal extension of tumor, a deeply invasive tumor was suspected on US but was not found on pathologic examination. In 12 superficially invasive tumors, the continuity of the demarcating subendometrial halo was intact in nine and incomplete in three. In six patients with deeply invasive tumors, this zone was partially disrupted in four, totally disrupted in one, and intact in one. Errors of estimation of the depth of myometrial invasion on US most frequently occurred when a tumor had a significant intraluminal polypoid extension. Demonstration of a subendometrial halo usually indicated superficial invasion, whereas the absence of a halo was frequently associated with deep invasion.

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.

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.

Improved determination of spin density, T1 and T2 from a three-parameter fit to multiple-delay-multiple-echo (MDME) NMR images

A method is presented for simultaneously determining values of relative hydrogen spin density Nr, T1 and T2 from a single set of NMR image intensities acquired in a short imaging time. Present methods use separate acquisitions and data sets to determine all three parameters. In the method presented, multiple-echo data are collected at multiple delays in virtually the same imaging time used to obtain T1 and a T2-weighted Nr from a separate saturation recovery (SR) T1 measurement. All three parameters are then determined by a three-parameter fit of a derived signal intensity equation to these multiple-delay-multiple-echo (MDME) data. This provides an inherent correction of Nr for T1 and T2 weighting without the use of sequences with TD greater than 5T1, and without further data collection for a separate T2 measurement. It also provides an effective reduction in the noise of the separate T2 measurement. A three-parameter fit to MDME data appears to be superior to the separate T1 and T2 measurements currently used to determine all three parameters. Calculations performed on CrCl3 solutions produced T1 values from 21 ms to 3.4 s, T2 values from 6 to 714 ms, and standard errors as low as 0.33%, with a net imaging time of the order of that required for routine low-noise signal intensity imaging. The method could potentially be used in NMR spectroscopy to give similar benefits.

Response of patients to informed consent for excretory urography

The desirability of obtaining written informed consent for low-risk radiologic procedures has been the subject of controversy. A group of 80 patients was studied to evaluate the effect of informed consent for excretory urograms on: (1) incidence of contrast reactions; (2) discomfort during the procedure; (3) level of patients' anxiety before and after the procedure; (4) patients' perception of the procedure; and (5) desirability of informed consent from the patients' viewpoint. Results revealed no statistically significant difference between the 2 groups in the incidence of reactions, discomfort, perception of the examination, or anxiety level prior to the procedure. The informed consent group had a statistically greater factual knowledge of the procedure evaluated objectively (P less than 0.01). Of the patients who received the written consent form, 83% regarded it as helpful and none viewed it as harmful or refused the examination. In the control group, 32% desired more information.

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.

Magnetic resonance imaging of the breast: functional T1 and three-dimensional imaging

Thirty-two patients with breast abnormalities and 10 normal volunteers were examined with magnetic resonance imaging (MRI) utilizing a 0.5-Tesla superconducting magnet imaging system. Sagittal, coronal, and transverse breast imaging with the 50-cm body coil and with a specialized 16 X 8 cm breast coil allowed the evaluation of a single breast. Soft-tissue contrast was clearly apparent using proton density-weighted, T1 weighted, calculated T1 images. In addition, the feasibility and potential clinical utility of three-dimensional color imaging was evaluated using computer-based interactive algorithms for edge detection of the breast and for abnormal structures within the breast. MR scan data were correlated with conventional xeromammography, ultrasound, clinical, data, and pathological specimens. In vivo and in vitro breast imaging was evaluated in a feasibility study. It was concluded that MR imaging is a most sensitive modality for the identification of breast lesions, especially when the adjacent normal tissue is primarily fat. There does appear to be significant overlap in soft-tissue contrast when the adjacent breast parenchymal tissue is fibrocystic in nature. The T1 parameter may be a relatively specific measure for identifying a malignant breast mass.

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.

Medical image management

Medical image management is becoming increasingly complex as additional data are produced by equipment using digital techniques. As the requirements to store and display these images increase, the following questions become important: (a) What methods can be used to ensure that information given to the physician represents the originally acquired data? (b) What technology and methods are needed to guarantee that information is presented in a timely fashion when requested? (c) How can an image archiving and transmission system be designed to protect the patient's rights of confidentiality? The authors discuss the legal implications of digital archiving of image information and propose some approaches to designing systems that provide the most information to the physician and yet attempt to minimize infringement of the patient's rights.

Ectopic pregnancy: a malpractice paradigm

Subtle sonographic findings and other nonspecific clinical presentations often lead to missed diagnoses that can have significant legal implications. This communication discusses current diagnostic and laboratory methods used to evaluate patients with a suspected ectopic pregnancy in light of the concepts of "missed lesions" as they relate to negligence and malpractice theory.

MR imaging of the adrenals: correlation with computed tomography

The purpose of this study was to evaluate the role of magnetic resonance (MR) imaging in adrenal disease based on correlative imaging with CT. Fifty lesions in 36 patients with a variety of adrenal diseases were evaluated, at 0.5 T using spin echo (SE) multislice short repetition time (TR) and SE multislice multiecho long TR sequences. It is concluded that MR is capable of identifying most adrenal abnormalities previously detected by CT. The results suggest that MR has a greater specificity for mass lesions and might be useful to differentiate nonfunctioning adenomas from functioning adenomas, metastasis, pheochromocytomas, cysts, and intraadrenal hemorrhage. Magnetic resonance imaging also has the potential to detect aldosteronomas by increased signal intensity in addition to contour distortion using long TR/echo time sequences. The ability to perform multiplanar imaging and the presence of superior contrast as compared with CT are useful for the assessment of origin and extension of large lesions and the detection of pheochromocytomas in complex cases. Considering MR's limitations, we believe that at present its major role in evaluation of adrenal disease should be complementary to CT.

Spin echo technique selection: basic principles for choosing MRI pulse sequence timing intervals

Several "rules of thumb" are presented here to guide the MRI practitioner in spin echo technique selection and in the interpretation of pathologic changes.

Enhancement of red blood cell proton relaxation with chromium labeling

Nuclear medicine has utilized chromium (Cr) for decades to label red blood cells (RBCs). The purpose of this project was to determine whether sufficient paramagnetic Cr could be bound to red cells to influence proton relaxation significantly. We demonstrated that the T1 and T2 of RBCs can be substantially shortened by labeling them with paramagnetic Cr. Proton relaxation enhancement occurs when red cells are incubated with sodium chromate (VI) over a concentration range of 0.10 mM to 31.6 mM. Labeling with Cr at a concentration of 31.6 mM shortened the T1 of packed cells from 714 msec to 33 msec, and the T2 from 117 msec to 24 msec, as compared with nonlabeled red cells. In vitro hemolysis was significantly increased after labeling at 31.6 mM, but not at lower concentrations. Cr-induced proton relaxation enhancement varied with RBCs from different species, temperature, pH, and length of incubation. T1 values of kidneys containing labeled red cells (303 msec), or labeled cells diluted 10-fold with nonlabeled cells (479 msec), were decreased compared with kidneys containing only nonlabeled cells (600 msec). Finally, preliminary data indicate that the signal intensity of perfused renal tissue is significantly influenced in vivo by infusion of Cr-labeled RBCs. This study demonstrated that Cr labeling of RBCs sufficiently enhances red cell proton relaxation to provide excised organs containing red cells, of which 10% have been Cr-labeled, with shorter T1 and T2 values than organs containing nonlabeled cells. In addition, the ability of labeled cells to alter signal intensity in vivo suggests that Cr may have the potential to become an MRI contrast agent.

Early changes in experimental hydrocephalus

In acute obstruction of the cerebral spinal fluid (CSF) absorption pathways, fluid is produced more rapidly than it is absorbed, and the ventricles enlarge proximal to the obstructions. Communicating hydrocephalus results from a difference between the rates of production and absorption of cerebrospinal fluid. In animals with chronic communicating hydrocephalus, the initial pathologic changes appear to involve the periventricular tissue near the angles of the lateral ventricles. The present investigation was designed to identify the various changes associated with the production of communicating hydrocephalus in acutely hydrocephalic preparations and to relate these findings to those found in experimental animals with chronic communicating hydrocephalus. The results of this study seem to confirm that the changes noted in the chronically hydrocephalic animals occur as early as 12 hours after the restriction of the normal flow of CSF.

Influence of NMR measuring sequences and gradient variation on signals from flowing systems. Magnetic resonance tomography on experimental models

The influence of flow on MR tomography images and signal intensities has been studied using experimental model tubes and an aqueous NiCl2 solution having the same relaxation time as human blood. We applied the inversion recovery (IR) and the spin-echo (SE) sequence on a .15T MR tomography system. The influence of RF pulse distance (tau) in the IR and SE experiment as well as the influence of magnetic z-gradient strength on the flow images has been investigated. IR images revealed that signals from flowing systems recover more rapidly due to influx of non-inverted longitudinal magnetization into the scan slice. SE images in presence of flow are characterized by signal intensity loss with increasing time caused by the outflow and dephasing of transverse magnetization. With increasing strength of the z-gradient, the MR signals of flowing fluids decrease drastically. Thus for detection of flow, all the above mentioned parameters are of importance.

Cerebrospinal fluid pressure alterations in experimental communicating hydrocephalus. Response of cerebrospinal fluid pressure to increase in arterial carbon dioxide tension

The response of cerebrospinal fluid (CFS) pressure to increased arterial carbon dioxide tension (PCO2) was evaluated in 5 control animals and 7 animals with experimentally induced communicating hydrocephalus. The CSF pressure in control dogs increased moderately in response to PCO2; in dogs with hydrocephalus, an increase in PCO2 produced a pronounced increase in CSF pressure accompanied by a simultaneous decrease in cerebral perfusion pressure. Progression of hydrocephalus can be explained by increased intracranial pressure, periventricular edema and cerebral ischemia.

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.