Laser spectroscopy steered C-labelling of plant material in a walk-in growth chamber.

Rationale: Carbon-13 ( C)-labelled plant material forms the basis for experiments elucidating soil organic carbon dynamics and greenhouse gas emissions. Quantitative field-scale tracing is only possible if plants are labelled homogeneously in large quantities. By using a laser spectrometer to automatically steer the isotopic ratio in the chamber, it is possible to obtain large amounts of homogeneously labelled plant material.

Effects of soil organic matter properties and microbial community composition on enzyme activities in cryoturbated arctic soils.

Enzyme-mediated decomposition of soil organic matter (SOM) is controlled, amongst other factors, by organic matter properties and by the microbial decomposer community present. Since microbial community composition and SOM properties are often interrelated and both change with soil depth, the drivers of enzymatic decomposition are hard to dissect. We investigated soils from three regions in the Siberian Arctic, where carbon rich topsoil material has been incorporated into the subsoil (cryoturbation).

A computer utility for automated retrieval of radiology reports.

Objective: Many radiology information systems (RISs) installed during the 1980s have a user interface that is crude by today's standards. We explored improving this user interface by using the local processing power of the personal computer. In this article we describe a computer program that significantly enhances the ease of report retrieval by automating much of the interaction with our RIS, which is IDXrad.

Echocardiography of the right side of the heart.

Echocardiography has not only revealed the morphologic aspects of the right-sided cardiac structure but has, through the use of pulsed and color Doppler imaging, provided a whole new level of certainty in the diagnosis of cardiac disease. The structure and function of the right-sided chambers are now far better appreciated since this technique has become more widely used for early clinical diagnosis of right-sided cardiac disease.

The prospect of expert system-based cognitive support as a by-product of image acquisition and reporting.

In order for computer-based decision-support tools to find routine use in the everyday practice of clinical radiology, further development of user interface and knowledge content are required. In an ideal interface, the interaction between the radiologist and the computer would be minimized and painlessly integrated into existing work patterns. In this article, we explore some of the ways that pre-existing computer interactions in the processes of image acquisition and reporting can be used to feed case information into an expert system and thereby allow users to acquire advice from it in an automatic fashion.

Transesophageal echocardiographic guidance of transcatheter closure of atrial septal defect.

Transcatheter closure of atrial septal defect (ASD) was accomplished in 10 of 11 patients aged 13 months to 46 years (weight range 11 to 77 kg). Transesophageal echocardiography (TEE) was used simultaneously with fluoroscopic imaging in 4 of these patients aged 4.5 to 46 years (weight range 19 to 77 kg).

Observer variability in echo-Doppler measurements of portal flow in cirrhotic patients and normal volunteers.

The intraobserver and interobserver variability in measuring the portal vein flow by the echo-Doppler technique was evaluated in a blind controlled study. A total of 22 cirrhotic patients and 14 normal volunteers were examined by two skilled operators using duplex Doppler within a period of 1-3 mo (6 cirrhotics and 7 normal volunteers by both observers). Area, mean velocity, and flow were measured (4 measurements: A, B on day 1; C, D on day 2).

Exploring subjective vs. objective issues in the validation of computer-based critiquing advice.

Evaluation is an important part of the development of computer-based medical expert systems. Such evaluation may be particularly difficult when judging a critiquing system which responds to a proposed management strategy with a discussion of the advisability of that approach. DxCON is an expert system which produces a prose critique discussing the radiologic workup of obstructive jaundice.

Optimizing radiologic workup: an artificial intelligence approach.

The increasing complexity of diagnostic imaging is presenting an ever expanding variety of radiologic test options to clinicians. As a result, it is becoming more difficult for referring physicians to select an appropriate sequence of tests. The current economic pressures on medicine make it particularly important that resources be used judiciously.

Normal instability of the hip in the neonate: US standards.

In recent years, the use of real-time ultrasonography (US) has enabled dynamic evaluation of the infant hip through a range of motion and stress. Preliminary experience has suggested that a certain amount of instability in the hips of newborns is normal, but no standards have been established. In this study, a group of term neonates whose physical examinations were normal were examined with US on the 1st and 2d days of life.

Unusual causes of increased vascular impedance in renal transplants: duplex Doppler evaluation.

Duplex Doppler ultrasound (US) examination of the renal vasculature has proved valuable in assessing the kidney transplant. The normal renal allograft exhibits low-impedance arterial inflow similar to that seen in the normotopic kidney. The authors and others previously reported that a high vascular impedance, defined as either a pulsatility index (PI) greater than 1.

Investigation of Doppler waveforms in porcine renal allografts: Doppler-pathologic correlation.

A porcine model was devised to investigate Doppler waveforms in dysfunctional renal allografts. NIH miniature pigs served as allografts donors and recipients. Renal transplantation was effected into the recipient pelvis while the left normotopic kidney was subjected to warm ischemia in order to induce acute tubular necrosis (ATN).

HYDRA: a knowledge acquisition tool for expert systems that critique medical workup.

HYDRA is a computer-based knowledge acquisition tool under development to assist in the creation of expert systems which critique medical workup. To use HYDRA, a domain expert first outlines the recommended approaches to the workup of a chosen medical problem, using the Augmented Transition Network formalism. From this model, HYDRA produces a list of the various conditions for which critiquing comments may be required to react to all possible approaches that might be proposed by the user of the critiquing system.

Doppler signal quantitation in renal allografts: comparison in normal and rejecting transplants, with pathologic correlation.

Quantitative duplex Doppler sonography was performed in 55 renal transplant patients during 54 independent episodes of acute rejection, three episodes of chronic rejection, three episodes of acute tubular necrosis (ATN), and 23 occasions of normal graft function. Doppler signals were obtained from four arterial sites in each kidney. Nine patients, in whom signals were absent, were subsequently shown at nephrectomy to have absence of perfusion resulting from severe acute vascular rejection.

Computed tomographic (CT) guided percutaneous fine-needle aspiration biopsy: the Yale experience.

Fifty-one CT-guided percutaneous fine-needle aspiration biopsies (PFNAB) were performed on 46 consecutive patients over 15 months. Cytologies were obtained to identify primary or secondary malignancy in the abdomen, pelvis, retroperitoneum, bone, and paraspinal region. Adequate cytologic material was obtained in 50 of 51 biopsies.

Quantitative US attenuation in normal liver and in patients with diffuse liver disease: importance of fat.

Two methods are used to estimate ultrasound attenuation in liver. These were based on amplitude change and frequency change as a result of depth dependent attenuation. Evaluation of the two methods against a family of calibrated phantoms yielded correlation coefficients of 0.

Liver transplant recipients: portable duplex US with correlative angiography.

Twenty patients, aged 4 months to 58 years, were evaluated for liver transplantation by duplex sonography, and 15 transplantations were completed; 42 postoperative examinations were performed. Sonographic findings were correlated with seven preoperative and five postoperative angiographic evaluations. Preoperative duplex US findings included tumors, portal vein occlusion, varices, biliary obstruction, and variant vascular anatomy.

Renal allografts in acute rejection: evaluation using duplex sonography.

Sixty-nine duplex sonographic studies were performed in 24 patients who had received renal allografts. After a prospective qualitative analysis of the Doppler waveforms, results were correlated with biopsy material and each patient's clinical course. Increased pulsatility of the Doppler waveform of intrarenal arterial flow constituted an abnormal study, indicating acute rejection.

Duplex Doppler: identification of cavernous transformation of the portal vein.

Three cases of cavernous transformation of the portal vein are presented, which emphasize the value of duplex Doppler sonography in the recognition of abnormal vascular structures. In all three cases, cavernous transformation was unsuspected; in two, the initial sonographic or CT examinations were interpreted incorrectly. These cases suggest that the combination of characteristic pulsed-Doppler waveforms and the real-time appearance of cavernous transformation is virtually diagnostic.