Evaluating contrast-enhancing brain lesions in patients with AIDS by using positron emission tomography.

OBJECTIVE: To determine whether a noninvasive method for evaluating contrast-enhancing brain lesions in patients with the acquired immunodeficiency syndrome (AIDS) can accurately differentiate between lymphoma and nonlymphoma diagnoses. This method is based on Toxoplasma serologic testing and positron emission tomography. DESIGN: Prospective, nonrandomized, criterion-standard clinical study. SETTING: An academic center in the mid-southeastern United States. PATIENTS: 20 patients with AIDS and contrast-enhancing brain lesions. INTERVENTIONS: Positron emission tomographic scanning and Toxoplasma serologic testing. MAIN OUTCOME MEASURE: Diagnoses were confirmed by clinical response, autopsy, or brain biopsy. RESULTS: Eight patients had a confirmed diagnosis of toxoplasmosis, six had lymphoma, four had other diagnoses, and two were not evaluable. Seven of eight patients with toxoplasmosis had positron emission tomographic scans; all of these scans showed hypometabolic lesions consistent with a nonlymphoma diagnosis. The six patients with lymphoma all had hypermetabolic lesions on positron emission tomographic scans. The difference between these two sets of results was statistically significant (P < 0.001, Fisher exact test, two-tailed). The anti-Toxoplasma titer was greater than or equal to 1:4 in all patients with confirmed toxoplasmosis who had serologic testing and in three of six patients with lymphoma. CONCLUSIONS: Evaluating contrast-enhancing brain lesions in patients with AIDS by using Toxoplasma serologic testing and positron emission tomography can accurately guide therapy and obviate the need for most brain biopsies in these patients. A larger, national, multicenter study is needed to confirm our findings and to determine the effect of earlier diagnosis and treatment on morbidity and mortality in patients with AIDS and primary central nervous system lymphoma.

Design and evaluation of a flow phantom.

RATIONALE AND OBJECTIVES: We constructed a near-anatomically correct large-vessel phantom to perform repeatable flow dynamics research examinations by angiography, magnetic resonance (MR) angiography, and computed tomography (CT) angiography. METHODS: An internal carotid artery was constructed within a head phantom. The internal carotid artery branches into a middle and an anterior cerebral artery; the former trifurcates and ends in the superior sagittal sinus, and the latter ends in the inferior sagittal sinus. A transverse and sigmoid sinus drains the model. All four vessels connecting the arterial and venous vessels have variable flow-constricting ligatures placed around them. These ligatures are accessible on the skull surface. The skull cavity is filled with a silicone polymer that is isodense to brain on CT scans and isointense on most MR images. RESULTS: The flow in the phantom's vessels may be varied in a repeatable manner. Multiple scan sequences may be performed without the image degradation caused by patient motion. The homogeneity of the filler polymer allows visualization of flow-related artifacts that may be hidden by complex human anatomy. CONCLUSION: Preliminary images of each modality show promise for use of the phantom in imaging research on large-vessel flow dynamics.

Quality of clinical MR images and the use of contrast agents.

Attempts to optimize the quality of magnetic resonance images must balance the competing needs for high spatial resolution, high signal-to-noise ratio, a large number of sections, and a reasonable imaging time. These factors, which determine the ultimate image quality, are affected by a number of variables, including the field of view, the matrix and pixel size, choice of repetition time and echo time, section thickness, and the number of signals averaged. The manner in which these variables interrelate and their effect on the ultimate image quality are important in order to craft the most appropriate examination for each individual patient. A second major effect on soft-tissue contrast is the use of paramagnetic agents. The spectrum of utility of these agents within the central nervous system and the body is increasing. A large number of new agents are also being investigated, primarily for use outside the central nervous system.

Efficacy of seven retrograde tracers, compared in multiple-labelling studies of feline motoneurones.

The labelling efficacies of 7 retrograde tracers were evaluated following cut nerve exposure or intramuscular injection into the serially compartmentalized neck muscle, biventer cervicis. Tested tracers included Fast Blue (FB), Fluorogold (FG), dextran conjugated to fluorescein (FD), dextran conjugated to rhodamine (Fluororuby (FR), 3000 and 10,000 MW), fluorescent latex microspheres, horseradish peroxidase coupled to colloidal gold, and 1,1'-dioctadecyl-3,3,3',3'-tetramethyl indocarbocyanine perchlorate (DiI). In 2 animals, horseradish peroxidase was also employed and spinal cords were processed for peroxidase activity to evaluate its effect on the appearance of cells labelled with fluorescent tracers. Four tracers, FB, FG, FD and FR, could be observed in motoneurones under the conditions of our study. FB and FG labelled comparable numbers of motoneurones following cut nerve exposure, but dissimilar numbers following intramuscular injection. FG diffused extensively following injection and was found in motoneurones not only in the appropriate ipsilateral segment but also adjacent ipsilateral and contralateral segments. Intramuscular injections of FB usually labelled fewer cells than cut nerve exposure, but evidence for spurious labelling following intramuscular injection could also be found. FD or FR labelled motoneurones following cut nerve exposure but not following intramuscular injection. The conjugated dextrans labelled more variable numbers of cells than FB or FG, but the labelled cells had similar patterns of distribution. The remaining tracers were ineffective as retrograde markers in our study, and the possible reasons for these failures are discussed.

Magnetic resonance imaging of neurocysticercosis.

Neurocysticercosis (NCC) is involvement of the central nervous system (CNS) by the porcine tapeworm, common in developing countries with poor sanitation. The disease has been noted increasingly in nonendemic areas because of travel and immigration from affected regions. The magnetic resonance (MR) appearance can be characteristic, with single or multiple cysts and varying degrees of wall enhancement and surrounding edema, depending on the stage of the life cycle of the larva and its associated cyst.

Magnetic resonance angiography techniques.

After a radio frequency pulse, the decay of the magnetic resonance (MR) signal is described by two relaxation processes, T1 and T2. T1 describes the rate at which the magnetization realigns itself along the external magnetic field direction (ML), and T2 describes the rate of decay of the magnetization component along the transverse axis (MT). Magnetic resonance angiography (MRA) sequences have been developed that encode flow as changes in the apparent T1 or T2 of the moving blood relative to stationary tissues. MRA sequences typically use either time-of-flight (TOF) techniques to encode T1 or phase-contrast techniques to encode T2. TOF techniques encode flow as an apparent T1 shortening through the wash-in of fully relaxed blood from outside the image volume. The shorter T1 produces an enhancement of vascular structures relative to stationary tissues. TOF methods may use either sequential two-dimensional, three-dimensional, or multi-slab three-dimensional imaging sequences to produce a three-dimensional MRA data set. Phase-contrast methods use additional magnetic field gradients to encode flow as shifts in the phase of MT. Both TOF and phase-contrast methods use maximum intensity projection (MIP) images displayed in a cine format to aid in the visualization of three-dimensional vascular structures.

Clinical impact of picture archiving and communication systems: evaluation of a prototype system.

Opinion surveys were gathered before and 6 months after installation of a prototype picture archiving and communication system (PACS) (PACS/1, Siemens Medical Systems, Iselin, NJ). Median turnaround times and the percent of delayed or missing reports were calculated for 1,026 baseline and 8,438 follow-up studies at 6 months. Neuroradiological (neuro) computed tomography (CT) used PACS, while neuro magnetic resonance (MR), body CT, and body MR served as controls. The opinion surveys showed improved service in all categories, including those not directly affected by PACS. PACS images favorably impressed 86% of respondents, but most considered the system too slow, unreliable, and the storage capacity too low. A majority of 81% recommended against purchase of PACS now. There was an overall increase in the median report turnaround time for both neuro CT and the controls. Neuro CT showed a 41% decrease in delayed or missing reports, but controls also showed similar decreases. The effects of this prototype PACS on turnaround time or on report delivery could not be distinguished from section-wide changes in CT and MR services. Future improvements in PACS should vigorously address increased speed, reliability, and storage capacity.

Magnetic resonance perfusion/diffusion imaging of the excised dog kidney.

RATIONALE AND OBJECTIVES: The authors developed a model of tissue capillary beds applicable to perfusion/diffusion imaging with magnetic resonance imaging (MRI). The model consists of a formalin-fixed excised dog kidney attached to a variable speed pump. With this system, it is possible to perfuse the kidney at selected rates. METHODS: Using the intravoxel incoherent motion model (IVIM), the apparent diffusion coefficient (ADC), diffusion coefficient (D), and perfusion fraction (f) were computed for a region of interest (ROI) in the renal cortex and in the medulla of seven kidneys, one of which was injected with a vasodilator before fixation. ADC and D values were computed for both cortex and medulla. These values were normalized to zero flow and plotted against renal perfusion. The perfusion fraction f was expressed in percent and was not normalized to zero flow. RESULTS: Normalized ADC and f were correlated with tissue perfusion rates using the Spearman rank-sum test (n = 18, rs greater than 0.5, P less than or equal to .02 for the standard preparation in both cortex and medulla), whereas normalized D (rs much less than 0.5) was uncorrelated for both preparations in cortex and medulla. CONCLUSIONS: The isolated perfused dog kidney is a useful model of tissue capillary beds for perfusion imaging technique development. The perfusion/diffusion-related parameters ADC and f increase as flow increases in the tissues, whereas D does not.

Gadolinium-enhanced MR angiography.

Experience in three patients (one each with meningioma, pineal tumor, and prominent jugular bulb) illustrates that magnetic resonance (MR) angiography can benefit from the administration of gadolinium diethylenetriaminepentaacetic acid. Data were acquired with a three-dimensional velocity-compensated (fast imaging with steady-state precession) sequence. MR angiograms were obtained with a ray projection algorithm by using maximum intensity values. Portions of the vascular anatomy--particularly venous structures and smaller arteries--were better portrayed on the postcontrast than on the precontrast angiograms. Enhancing lesions were also seen on the projection images. Enhancement of dura and extracranial tissues (sinus and nasal mucosa) can obscure vascular detail.

Computerized data base of teaching conference cases.

Conferences consisting of case presentation with discussion are a major tool in radiology resident teaching. We used a computerized data base to study the case mix at our teaching conference. At daily conferences from July 1984 to March 1985 each case was recorded as to patient name, identification number, date, type of conference, case presented, modality used, organ study, and diagnosis. Data were entered on a 256K IBM PC with two 360K disk drives running dBase II (Ashton-Tate). Use of a computer to store the information offered the advantage of rapid analysis of the data by type of study or region of interest. Initial use of the system has confirmed its utility in the areas of teaching file generation, monitoring of conference content, and as an aid in modifying the case content to represent more evenly the spectrum of disease found in a given organ or an organ system.

Image communications. What is needed and why.

Better communications are essential in the new medical environment. Methods to make more efficient the throughput in an existing department, foster confidence of patients, and improve the communications and efficiency of referring physicians are needed. The most difficult and thus the driving component of the new communications environment is image transmission. Concepts of picture archiving and communications systems, or PACS, arising from digital technology make possible unique and ubiquitous solutions to image communications. Better quality control and improved interpretation throughout the system, including the offices of referring physicians, will be possible. Radiologists are in a position to mold this new medical industry.

Salpingitis isthmica nodosa: radiologic and clinical correlates.

Salpingitis isthmica nodosa (SIN) is thought to be an inflammatory condition of the fallopian tubes and is strongly associated with infertility and an increased risk of ectopic pregnancy. The diagnosis is best made radiographically at hysterosalpingography (HSG), where the characteristic finding consists of multiple nodular diverticular spaces in close approximation to the true tubal lumen. We reviewed 1,194 HSGs performed over a five year period and identified 45 patients who had SIN (4%). There was a high rate of primary infertility (37.5%) and ectopic pregnancy (9.4%). Of 70 involved tubes, 62 (89%) had evidence of associated inflammation on historic, radiologic, surgical, or histologic grounds. We conclude that SIN is a disorder most likely acquired during the fertile years, and that the lesion is either a direct consequence of infection or that--once present--it predisposes the patient to subsequent infections.