Agronomic and environmental impacts of a single application of heat-dried sludge on an Alfisol.

A field experiment was conducted on Alfisols in South-West France to assess the agronomic and environmental impacts of a single application of heat-dried sludge pellets at 11.1 Mg dry matter ha-1. The sludge pellets, with a moisture level of 9.5%, were spread on an irrigated crop of maize (Zea mays L.). This treatment was compared with inorganic fertilization (urea and diammonium phosphate mixed with KCl). Soil properties, yield and the composition of maize and the quality of drained water were monitored over 1 year to detect any changes resulting from sludge application. Amongst several determined soil properties, only two were significantly modified by the sludge application: The nitric nitrogen stock of the soil was higher in the inorganic fertilized plot, whereas Olsen-P soil content was higher in the sludge-amended plot. Agronomic recovery rates of N and P added by sludge were high: For the first crop following application, total amounts of N and P supplied by the sludge had the same efficiency as approximately 45% of the N and P amounts supplied by inorganic fertilizer. This ratio was 7% for the N uptake by the second maize crop. The quality and quantity of maize were equally good with both types of fertilization. During the 2 years following sludge spreading, N leaching remained as low in the sludged plot as in the inorganically fertilized one. The Cu, Zn, Cr, Cd, Pb and Ni composition of the drainage water was affected by neither of the types of amendment. From the heavy-metal contents of the soil, water and maize monitored over 1 year in the field experiment and from literature data for cow manure and atmospheric emissions, a theoretical balance between crop soil heavy-metal input and output over one century was drawn up. The long-term impact of cow manure on Zn, Ni and Cr in soil is higher than that of the studied heat-dried sludge. Obviously, sludge tended to cause a strong increase in soil Cu storage, valued for these soils, which are otherwise very Cu deficient.

Preparing medical students for a filmless environment: instruction on the preparation of electronic case presentations from PACS.

RATIONALE AND OBJECTIVES: As the use of picture archiving and communication systems (PACS) expands and radiology departments become increasingly filmless, it will become increasingly necessary to teach physicians how to use PACS and download diagnostic images. The authors developed an instruction method in which medical students enrolled in a radiology clerkship were taught how to use the PACS, download digital images, and incorporate them into an electronic case presentation. The feasibility and potential benefits of this instructional method were studied prospectively. MATERIALS AND METHODS: Between June and October 1999, all 36 medical students enrolled in Harvard Medical School's core radiology clerkship at Massachusetts General Hospital, Boston, were required to give an electronic radiology case presentation with images downloaded from the departmental PACS. They were taught how to download images, edit them, and then import them into PowerPoint software. They were also given access to the hospital information system to obtain pertinent clinical information. At the formal presentations, the images were displayed with a liquid crystal display (LCD) projector. The students were surveyed on the Ist and last days of the clerkship regarding their learning experiences. RESULTS: Before the radiology clerkship, 81% of the students had never given an electronic presentation with computer and LCD projector, 83% had no PACS experience, and 56% had no PowerPoint experience. All students learned to prepare and deliver electronic presentations of radiologic cases downloaded from PACS. Their presentations were informative, innovative, and entertaining, and the images were well displayed. The students praised the instruction highly and thought their new skills would serve them well. CONCLUSION: Teaching medical students how to prepare and deliver electronic presentations of radiologic cases downloaded from PACS proved to be very feasible and well appreciated by the students.

Pre-operative localization of parathyroid adenomas: a comparison of power and colour Doppler ultrasonography with nuclear medicine scintigraphy.

AIM: To compare power and colour Doppler ultrasonography (US) with nuclear medicine scintigraphy (NM) in the preoperative localization of parathyroid adenomas in patients with primary hyperparathyroidism (PHPT). MATERIALS AND METHODS: Thirty-one patients with biochemical evidence of PHPT underwent pre-operative US and NM for parathyroid adenoma localization. Both studies were interpreted independently without prior knowledge of the other study's findings. All patients had surgical removal of the parathyroid adenoma utilizing standard neck exploration or minimally invasive unilateral surgical techniques with rapid serum assay of circulating parathyroid hormone levels. RESULTS: All patients had single parathyroid adenomas at surgery. Prospective sensitivities for US, NM and both studies combined were 65%, 68%, and 74%, respectively, with a positive predictive value of 100% each. The adenoma was localized by only one imaging modality in 16% of cases. CONCLUSIONS: US and NM provide complementary roles in the pre-operative localization of parathyroid adenomas in patients with PHPT.

Advances in nuclear medicine: current concepts.

As described above, many scintigraphic studies have recently become available which provide vital clinical information in a wide variety of diseases. The future of nuclear medicine also appears bright. Modifications to current gamma cameras will likely occur in the next few years to replace sodium iodide crystals with new scintillators like oxyorthosilicates which have better imaging characteristics for both single photon and positron-emitting radionuclides. Ongoing computer improvements will allow improved reconstruction and processing with newer systems already capable of advanced iterative reconstruction algorithms. Development of new radiopharmaceuticals is progressing at a rapid pace, with emphasis on new tracers that can provide information about diseases at the molecular level, such as receptor imaging agents. In addition, radiolabeled tracers for therapeutic purposes will continue to progress, including monoclonal antibodies labeled with beta emitters. Overall, nuclear medicine will continue to evolve in many new directions and provide useful functional imaging data about a variety of different organ systems and diseases.

Diagnosis of pneumoperitoneum on supine abdominal radiographs.

A blinded, retrospective study was performed to determine the value of supine abdominal radiographs in diagnosing pneumoperitoneum. Supine films from 44 cases of pneumoperitoneum were randomly interspersed among supine films from 87 control subjects without free air, and the films were reviewed for the presence or absence of various signs of pneumoperitoneum, including Rigler's sign (gas on both sides of the bowel wall), the falciform ligament sign (gas outlining the falciform ligament), the football sign (gas outlining the peritoneal cavity), the inverted-V sign (gas outlining the medial umbilical folds), and the right-upper-quadrant gas sign (localized gas in the right upper quadrant). One or more of these signs were present in 26 cases (59%) of pneumoperitoneum, including the right-upper-quadrant gas sign in 18 cases (41%), Rigler's sign in 14 cases (32%), and the falciform ligament and football signs in one case each (2%). Unfortunately, there were frequent errors in the interpretation of the right-upper-quadrant gas sign and Rigler's sign, with a total of 11 false-positive cases (13%). Further analysis of the true-positive right-upper-quadrant gas signs showed that these gas collections were always triangular or linear with an inferolateral to superomedial orientation and, if triangular, a concave superolateral border. In the true-positive Rigler's signs, the bowel wall thickness ranged from 1 to 8 mm, whereas the false positives all had a bowel wall thickness of 1 mm or less. Proper interpretation of the various signs of pneumoperitoneum on supine films should lead to more accurate diagnosis of this condition.

An automated iterative algorithm for the quantitative analysis of in vivo spectra based on the simplex optimization method.

The success in utilizing in vivo NMR to identify and/or monitor metabolic abnormalities will be determined in large part on the reliability with which the spectral parameters of the metabolites present can be measured. For these reasons it is clear that there is a need for the development of algorithms with which to obtain quantitatively reliable estimates of the spectral parameters of the peaks present. In this report we describe an adaptation of the simplex algorithm which we have found useful in fitting in vivo spectral data in the frequency domain. This simplex algorithm was implemented on an IBM-PC AT compatible computer. We evaluated the simplex algorithm on three representative kinds of spectral data: a simulated spectrum, 31P spectrum of normal calf muscle, and the 31P spectrum of a pediatric patient with a brain tumor. In each case we generated a set of spectra by adding varying amounts of noise. On the basis of our simulations and the two examples discussed, we conclude that the simplex method generates parameters which are reliable estimates of the areas of the peaks present when the signal-to-noise is above 8:1 for phosphocreatine. We found that the speed of convergence of the algorithm was improved by overestimating the linewidths of the peaks present. We also found that the method converged more rapidly in the presence of a moderate amount of noise. We conclude that the algorithm described here can provide a robust method with which to analyze in vivo spectra in a quantitative manner. Because the method requires little user intervention, it lends itself to implementation in a semi-, or fully, automated fashion.