Value of polydirectional tomography in the assessment of the postoperative spine after anterior decompression and vertebral body autografting

With the growing number of orthopedic reconstructive spinal procedures, the use of bone grafting has steadily increased in the past decade. An understanding of the biology of bone grafting is essential for both the clinician and radiologist. Despite the advent of computed tomography and magnetic resonance imaging, conventional polydirectional tomography remains an important tool in the evaluation of vertebral body autografts. Trispiral or hypocycloidal tomography plays a valuable role in the assessment of bone graft fusion and possible complications, especially in the presence of metallic fixation devices. We present our imaging experience derived from 375 patients with cervical, thoracic, or lumbar anterior spinal fusion. True graft complications occurred in 27 patients (7%) and consisted of fracture (4%), malpositioning (3%), and infection (<1%).     

The pros and cons of fecal occult blood testing for colorectal neoplasms

Testing feces for occult blood is widely recommended as a means of detecting subclinical colorectal tumors. Guaiac tests such as Hemoccult^® are the most widely used, but chemical sensitivity is relatively low and the tests are affected by dietary peroxidases, the state of fecal hydration, and certain drugs. The newly devised HemoQuant^® and immunologic techniques appear more sensitive and specific, but they require further evaluation before widespread clinical usage can be recommended.Occult blood screening has both merits and weaknesses. Testing does uncover subclinical colorectal cancer, often at a relatively early stage, but whether this actually improves the prognosis remains to be proven. Benign neoplastic polyps are also detected, although it is debatable whether this is a valid rationale for screening. Test sensitivity for malignancy varies from good to moderate, but is poor for benign polyps. Specificity is usually around 97%–98%, yet the predictive value of a positive test for cancer is only about 10%: hence most test-positive individuals are needlessly subjected to invasive colonic investigations. Reported figures on public compliance with occult blood testing vary widely from excellent to poor. Published costs of screening are usually quite low, but these overlook important indirect and hidden expenses and are therefore misleading.On balance, the problems of occult blood testing currently appear to outweight the merits. This could change, however, with the newer testing techniques and with awaited mortality data from controlled clinical trials now underway.     

Use of oxygen radical scavengers on autografted pig kidneys after warm ischemia and 48-hour perfusion preservation

Oxygen free radicals generated during the reperfusion of an ischemic organ may cause further cellular injury; removal of these oxygen radicals by scavengers protects tissue from reperfusion injury. Thus, oxygen radical scavengers could protect kidneys after warm ischemia and long hypothermic perfusion. Porcine kidneys were incubated at 37 degrees C for 45 minutes, placed on a pulsatile perfusion apparatus at 7 degrees C for 48 hours, and then autografted to iliac vessels. Superoxide dismutase (10 mg) and catalase (10 mg) in 10 mL of phosphate-buffered saline solution were infused into the renal artery during a three-minute interval before reperfusion. The kidneys treated with the superoxide dismutase-catalase solution had significantly improved function compared with controls receiving only phosphate-buffered saline solution. The mean (+/- SEM) serum creatinine level on postoperative day 5 was 510 +/- 100 mumol/L (5.75 +/- 1.12 mg/dL) (n = 12) vs the control value of 840 +/- 90 mumol/L (9.54 +/- 1.01 mg/dL) (n = 11). There was more extensive cellular damage in the control kidneys. This demonstrates the efficacy of oxygen radical scavengers in protecting pig kidneys after warm ischemia and prolonged preservation.     

Proficiency tests for radionuclide laboratories supporting the network of IMS stations.

A tailored proficiency test programme in high-resolution gamma-spectrometric analysis has been established for the radionuclide laboratories designated to support the verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). It entails certified reference samples that contain fission products relevant to the CTBT. The sample geometries and materials correspond to aerosol filter samples from the high-volume samplers of the radionuclide stations of the International Monitoring System (IMS) and the related calibration sources are matrix and geometry matched to the reference samples.     

Building bridges between neural models and complex decision making behaviour.

Diffusion processes, and their discrete time counterparts, random walk models, have demonstrated an ability to account for a wide range of findings from behavioural decision making for which the purely algebraic and deterministic models often used in economics and psychology cannot account. Recent studies that record neural activations in non-human primates during perceptual decision making tasks have revealed that neural firing rates closely mimic the accumulation of preference theorized by behaviourally-derived diffusion models of decision making. This article bridges the expanse between the neurophysiological and behavioural decision making literatures specifically, decision field theory [Busemeyer, J. R. & Townsend, J. T. (1993). Decision field theory: A dynamic-cognitive approach to decision making in an uncertain environment. Psychological Review, 100, 432-459], a dynamic and stochastic random walk theory of decision making, is presented as a model positioned between lower-level neural activation patterns and more complex notions of decision making found in psychology and economics. Potential neural correlates of this model are proposed, and relevant competing models are also addressed.